Aquarium Chemistry: The Nitrogen Cycle: New Developments and New Prospects

Aquarium Chemistry: The Nitrogen Cycle: New Developments and New Prospects

By Marco Colasanti

So far we have always thought of the nitrogen cycle as a series of linear reactions that conclude in a circle. But is it really a cycle? Important discoveries made in these recent years have drastically revolutionized this concept. In this article, I will try to discuss some of these research studies, with the intention and hope of being able to make this complex topic, understandable.

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Contents

1. The Canonical Nitrogen Cycle
2. Nitrogen Fixation and Ammonification
   1. Nitrogen fixation
3. Nitrification
4. Denitrification
5. New Developments and New Prospects
   1. AOA: Ammonium Oxidizing Archaeabacteria
6. DNRA
7. ANAMMOX: anaerobic ammonium oxidation
8. References
9. Acknowledgements
10. About the Author

The nitrogen cycle plays a highly important role in a closed environment like that of an aquarium. Due to its presence, it is possible keep the fish and invertebrates alive, in a small viable space, therefore it is fundamental to learn to know it, mainly in respect of the life forms that we nurture.

Until a few years ago, it was thought that the nitrogen cycle in its complexity, was a complete linear process. However, most recent scientific discoveries have greatly revolutionized our well-established knowledge on the nitrogen cycle and on the micro-organisms involved in such processes. As a matter of fact, the global cycle of nitrogen in the environment, particularly in that of marine, has been integrated with at least three new links which include:

1. the oxidation of ammonium by a particular group of micro-organisms, the archaeabacteria (AOA);
2. the anaerobic reduction of nitrates into ammonium ion (DNRA);
3. the anaerobic oxidation processes of ammonium (ANAMMOX).

In the first part of this article, I will try to review the essential and more predominant aspects of the nitrogen cycle: the transformation processes of the main components (atmospheric nitrogen, ammonium ion, nitrite, nitrate) and the role played by the bacterial species involved.

In the second part, new ways will be explored with particular reference on the role of bacteria, focusing on the implications that these new discoveries have brought in the global cycle of nitrogen.

The Canonical Nitrogen Cycle

Nitrogen (N) is an essential nutrient for all organisms, and it is a critical element of protein, vitamins and DNA, and is important in biochemical structures and process that define life.

Nitrogen exists in different states of oxidation and in many chemical forms and is quickly converted by the microorganisms both on earth and the sea.

In the marine environment, nitrogen is present in 5 forms:

1. Gaseous nitrogen (N₂), stable molecules that require specialized enzyme systems (present in some types of bacteria) for fixation and later use;
2. Ammonium ion (NH₄⁺), the most reduced natural specie of nitrogen, and the most biologically available in an oxygen-less environment;
3. Nitrate ion (NO₃^-), the most oxidized form of nitrogen and mostly usable in an aerobic environment;
4. Particulate organic nitrogen (PON), organic form of nitrogen predominant in sediments;
5. Dissolved organic nitrogen (DON), a rich mixture of molecules with a wide range of composition.

A complex network of reactions links these nitrogen forms in processes that as a whole, is called the nitrogen cycle (Figure 1). The greatest source of nitrogen comes in the form of inert gas N₂ (N ≡ N), representing 78% of the atmosphere. A small part of the atmospheric N₂ is fixed by particular bacteria called nitrogen-fixing (nitrogen fixation) and is reduced to ammonium ion (NH₄⁺) which can be easily usable for other organisms. In a marine environment which inhabited by particular bacteria, ammonium is quickly oxidized to nitrate in aerobic conditions (nitrification). Nitrate is then reduced again to an N₂ gas in anaerobic conditions (denitrification), thereby completing the cycle (Figure 1).

Figure 1. Diagram of the marine nitrogen cycle.

Nitrogen Fixation and Ammonification

Nitrogen fixation

The biological fixation of nitrogen can be synthetically represented by the following global formula:

N₂ + 8H⁺ + 6e^- → 2NH₄⁺

Which means that for each molecule of atmospheric nitrogen, 2 ammonium ions are formed with the absorption of 6 electrons and 6H+, this last process tends to increase the pH.

It is interesting to note that, ultimately, the ammonium ion in the water is in balance with ammonia (NH3) based on the following stoichiometry:

NH₃ + H₂O ↔ NH₄⁺ + OH^-

The concentration of the two chemical species relies largely on the pH, in short, the higher the alkalinity, the larger will be the quantity of ammonia; or proportion-wise, the lower the pH is (more acid), the larger will be the quantity of ammonium ion (less toxic than ammonia). As can be seen in Figure 2, in an average range of pH in the seawater, the percentage of NH4+ is higher (82-97%) compared to that of NH3 (3-18%).

As we have previously stated, the atmospheric nitrogen N₂, before being incorporated into the biological molecules, has to be reduced to NH₄⁺, through a series of reactions called biological fixation of nitrogen. Such reactions are catalyzed by a particular enzyme, nitrogenase, which is present in some nitrogen-fixing bacteria belonging mainly to Cyanobacteria phylum. One of the peculiar characteristics of this enzyme is that it comes irreversibly inhibited by the molecular oxygen (O₂); and since fixation is a process that happens in an aerobic environment, it creates an apparent paradox. In reality, cyanobacteria are able to negotiate the activities of nitrogenase, an enzyme which is essentially anaerobic, with the inevitable presence of oxygen (resulting from photosynthetic processes), through not yet well-known mechanisms. In the marine environment, the nitrogen-fixing bacteria (some of which also belong to Clostridium and Azobacter genera) can be found both in free form and in symbiosis with other organisms (ex. Sponge).

But what is the source of nitrogen in an aquarium? Certainly, the biological fixation of nitrogen is an extremely important process in the ocean, but it has a limited role in the tank.

Figure 2. pH-dependent concentration of NH₄⁺ and NH₃ in the seawater

The main source of nitrogen is obtained from the nourishment both of the fish and invertebrates, particularly in the form of protein and single amino acids, assuming they are directly administered into the tank. Even minor vitamins and other molecules like the DNA, contain nitrogen but the quantity is decisively less than that of protein's. In proteins, nitrogen forms a part of the framework and of some single amino-acids' lateral chains, as the tryptophan, asparagin, glutamine, lysin, arginine, histidine.

The oxidative degradation of amino acids leads to the release of ammonia nitrogen into the tank. In what way? On one hand, the protein ingested by the fish or by the other organisms are broken down into single amino acids. In turn, amino acids can be used to build new proteins within the organism or be oxidized to supply energy. The degradation of amino acids by the animals leads to the elimination of varied by-products. For example, the fish release nitrogen as ammonia, while the majority of organisms may release it in the form of uric acid (fowls, reptiles), or urea (humans). On the other hand, in the presence of a strong organic charge, protein and amino acids in waste products, in sediments and in organic decay are decomposed in a process called ammonification, carried out by particular decomposer bacteria which release ammonium into the water by degrading the aminoacidic nitrogen.

Nitrification

Nitrification occurs in two distinct stages:

1. oxidation of ammonium to nitrite (nitrosation) and
2. oxidation of nitrite to nitrate (nitration).

1) Nitrosation: in the first stage, ammonium ion is oxidized to nitrite in two steps:

1. The first step is catalyzed by the enzyme, monooxygenase which forms the hydroxylamine by using O₂ as oxidant:
   2NH₄⁺ + O₂ → 2NH₂OH + 2H⁺
2. In the second step, hydroxylamine is oxidized to nitrite by the enzyme hydroxylamine-dehydrogenase:
   2NH₂OH + 2O₂ → 2H⁺ + 2H₂O + 2NO₂^-

2) Nitration: the oxidation of nitrite to nitrate, which occurs through the activity of the nitrite oxidase enzyme, completes the process of nitrification:

2NO₂^- + O₂ → 2NO₃^-

The conventional view of nitrification occurs in the presence of oxygen and anticipates the oxidation of ammonium to nitrate based on the following global synthetic formula (see Figure 1):

2NH₄⁺ + 4O₂ → 4H⁺ + 2H₂O + 2NO₃^-

But who directs the music? The metabolic work of nitrification is entrusted to two groups of nitrifying bacteria:

1. bacteria which oxidize ammonium (ammonia-oxidizing bacteria or AOB), also called nitrous bacteria. They belong chiefly to the Nitrosococcus and Nitrosomonas species;
2. bacteria which oxidize nitrite (Nitrite-oxidizing bacteria or NOB) also called nitric bacteria. They form a part of the Nitrobacter, Nitrococcus and Nitrospina species.

The nitrifying bacteria are generally obliged aerobes and obliged chemoautorophs because they directly use CO₂ as a source of carbon, while organic substances can be toxic.

Denitrification

Here I describe the four stages of denitrification process in detail. The oxidation state of nitrogen is indicated by the enclosing parentheses, after the names of chemical species.

1. Reduction of nitrate (+5) to nitrite (+3). This reaction is catalyzed by nitrate reductase (NAR) which exists in the (internal) cytoplasmic part of bacterial membrane. Nitrate is carried within the bacterial cell by a specialized carrier (AP in Figure 3), defined as antiport because it exchange ion nitrate upon entry with the nitrite which is produced in the reaction and must be carried to the (external) periplasmatic space for the subsequent reaction.
   2NO₃^- + 4H⁺ + 4e^- → 2NO₂^- + 2H₂O
2. Reduction of nitrite (+3) to nitric oxide (+2). The nitrite which is now at the periplasmatic space is reduced by nitrite reductase (NIR), releasing nitric oxide (NO). NO is a remarkably important molecule, from the bacteria to humans (but this is another story).
   2NO₂^- + 4H⁺ + 2e^- → 2NO + 2H₂O
3. Reduction of nitric oxide (+2) to nitrous oxide (+1). NO is reduced by nitric oxide reductase (NOR) to nitrous oxide (also called nitrogen protoxide otherwise known as the laughing gas). Both oxides represent a strong stimulus to the reductase synthesis in the presence of nitrates and under anaerobic conditions.
   2NO + 2H⁺ + 2e^- → N₂O + H₂O
4. Reduction of nitrous oxide (+1) to gaseous nitrogen (0). The last reaction in the denitrification process is the reduction of nitrous oxide to molecular nitrogen in gaseous form by the nitrous oxide reductase. This reaction should complete the denitrification process and conclude the nitrogen cycle.
   N₂O + 2H⁺ + 2e^- → N₂ + H₂O

Denitrification is one of the key processes within the nitrogen cycle and anticipates the reduction of nitrates to gaseous nitrogen, passing through nitrite, nitric oxide (nitrogen monoxide) and nitrous oxide (nitrogen protoxide).

The global reaction of denitrification (without considering the organic molecular degradation eventually associated) can be synthesized with the following formula (for details see Figure 1):

2NO₃^- + 12H⁺ + 10e^- → N₂ + 6H₂O

Denitrification is mainly a heterotrophic option and occurs in anaerobic conditions. A wide range of bacteria called precisely denitrifying bacteria are able to carry out the entire sequence of reactions, being equipped with a complete enzyme apparatus.

The denitrifying bacteria are able to accomplish the anaerobic respiration of nitrates by using the nitrate in place of oxygen, as acceptor of the electrons released during the respiratory process. These bacteria possess special enzymes (Figure 3), as the nitrate reductase (NAR) and nitrite reductase (NIR), which allows the electrons to flow towards nitrate or nitrite, in the absence of oxygen. They are flexible enzymes which form in the cellular membrane only under anaerobic conditions: as a matter of fact, a part of NAR, the reductase synthesis is inhibited in the presence of oxygen.

Some bacterial species of the Pseudomonas, Thiobacillus, Paracoccus and Naisseria classes, are considered denitrifying.

Figure 3. Denitrification process on the bacterial membrane.

New Developments and New Prospects

The previous description represents a well-known scenario for a long time. In the course of the recent years however, our references concerning the nitrogen cycle have drastically changed to the extent that the principle of closed linear cycle itself is being questioned. This is because new reactions have been discovered and consequently new microorganisms that make the entire nitrogen cycle even more complex and twisted (Figure 4). In the second part of this article, I will try to clarify some important ways which will be inserted within the canonical nitrogen cycle:

1. Ammonium oxidation by a particular group of microorganisms, the archaeabacteria (AOA)
2. The anaerobic reduction of nitrates to ammonium (DNRA):
3. The anaerobic oxidation processes of ammonium (ANAMMOX)

AOA: Ammonium Oxidizing Archaeabacteria

Recently, new important components of nitrogen cycle, which form the part of the richer and diffused group of micro-organisms in the planet, the archaeabacteria, have been identified. In spite of the group's evolutive line being unclear, the archaeabacteria (Archaea or Archeobacteria) combined with the eukaryotes and with eubacteria, are some of the fundamental domains of the living beings.

The archaeabacteria, like the bacteria, consist of single cells without nucleus and in the past they were classified as prokaryotes together with the bacteria. Based on the DNA analysis, the archaeabacteria were re-grouped into three phyla: Crenarchaeota, Euryarchaeota and Korarchaeota. The Euryarchaeota bacteria are the most prominent and they include methane producers and holophiles. The Crenarchaeota bacteria include thermophilic microorganisms, while the Korarchaeota bacteria are less known because only their DNA is recognized but no microorganism has so far been isolated. Originally, it was thought that the archaeabacteria were just inhabitants of a harsh and most hostile environment on the face of the earth. The thermophiles can grow at a temperature higher than 100°C, the psychrophiles are those which grow at temperatures lower than -10°C, while the acidophilus and the alkaliphiles grow in extremely acidic or alkaline environments, respectively. Finally, the halophiles prefer the highly saline environment. Today, we know that archaeabacteria are present in all habitats: for example the Crenarchaeota bacteria are considered ubiquitous components of zooplankton.

In 2004, a particular gene called the ammonium mono-oxygenase (amoA) was discovered in marine Crenarchaeota, indicating the capacity to oxidize ammonium. The definite and convincing link between this new gene and the ammonium oxidation in archaeabacteria has been recently established in Crenarchaeota, the Nitrosopumilus maritimus, which was isolated from the water of aquarium. N. maritimus is chemoautrophic: as a matter of fact it grows with bicarbonate as the only source of carbon (organic carbon inhibits its growth) and converts NH₄⁺ in NO₂^- (green line in Figure 4 and Figure 7). Other archaeabacteria have been successively identified with this property and have been named as Ammonium oxidizing archaeabacteria (AOA). An accurate analysis of the AmoA gene in many archaeabacteria has revealed diverse isoforms of this gene, each one is associated to a microorganism which is present in different habitats (with little overlapping, for example, between sediment and water column). Symbiont archaeabacteria have also been identified, like for example the Cenarchaeum symbosiosum, a symbiont Crenarchaeota with a sponge. Surprisingly, it was observed that this archaeabacteria is not able to produce hydroxylamine as intermediate reaction (see the Nitrosation process in the BOX 2) indicating that ammonium oxidization occurs with a mechanism which is different from that of the classic nitrification. Finally, the most recent studies conclude that the majority of Crenarchaeota are AOA's and AOA's are microorganisms whose presence is numerically predominant in the ocean.

Figure 4.Nitrogen cycle integrated with recently discovered reactions. Nitrogen oxidation states are pointed out.

Figure 5. The life tree. Evolving lines of the main domains.

DNRA

During the recent years, the anaerobic reduction of nitrates/nitrite or, DNRA (acronym for Dissimilatory Nitrate/nitrite Reduction to Ammonium) has stirred up a certain interest as a relevant reaction both in the terrestrial and marine eco-systems. The reaction has been described in anoxic sediments and in the presence of bacteria of the Thioploca and Thiomargarita species. Both types of bacteria are able to concentrate nitrates within their own cells for the subsequent oxidation of sulphur-containing compounds in reduced form. In this way, they are able to reduce nitrate to ammonium passing through nitrite as an intermediary compound (blue line in Figure 4 and Figure 7). This reaction, although still needing clarification, would potentially supply nitrite and ammonium to the ANAMMOX reaction (see subsequent paragraph) in anoxic sediments.

ANAMMOX: anaerobic ammonium oxidation

As we have previously seen in the description of AOA and nitrification stages, ammonium oxidation is a strictly aerobic process. In reality, we have also seen that ammonium can be generated in hypoxic and anoxic environment (for example in sediments) through the re-mineralization of organic nitrogen process (ammonification), and/or the anaerobic nitrite reduction (DNRA). For many years, it has been thought that ammonium is inert in anaerobic conditions, which is to say, useless for living things. The problem, however, is that no bacteria that are able to metabolize ammonium without oxygen have been identified, especially due to the technical difficulty of cultivating in the laboratory bacterial strains with these characteristics. In 2008, many of these difficulties have been overcome and some laboratories were able to identify, cultivate and characterize some types of ANAMMOX bacteria (Acronym for ANaerobic AMMonium OXidation) which are capable of oxidizing ammonium to gaseous nitrogen (N₂) (red line in Figure 4 and Figure 7) by using nitrite as electron acceptor, instead of oxygen.

The first bacteria that are isolated in a marine environment belongs to the Scalindua species (Sc. sorokinii) although a probe regarding the presence of other species like Brocadia and Kuenenia, is being conducted. The common characteristic of these bacteria, unique in its class, is the presence of a specialized organelle called anammoxosoma which is surrounded by a particular lipid (fat) that contains hydrazine oxide reductase, an exclusive enzyme which is able to combine nitrite and ammonium is a single step (Figure 6). These bacteria use a rather complex mechanism that involves hydrazine as an intermediary. However, the following reaction, which is incomplete and stoichiometrically unprecise, can suggest the idea of an ANAMMOX process.

NH₄⁺ + NO₂^- → N₂ + 2H₂O

This reaction has been described for the first time in sediment samples taken from particular marine ecosystems (the Black Sea, for example). It has been observed that in those experimental conditions, the ANAMMOX process was responsible for the loss of 30-50% of inorganic nitrogen from the sea (in the form of N₂), significantly making it of the same level as the classic denitrification. But to analyze it closely, if we associate the above-mentioned DNRA process with ANAMMOX, we have a real and actual anaerobic denitrification, clearly not canonical. Indeed, DNRA supplies nitrite (as a reaction intermediary beginning from nitrate) and ammonium (the latter having been obtained also through organic nitrogen ammonification), and ANAMMOX transforms everything into gaseous nitrogen. A lovely and good denitrification, clearly with different mechanisms and bacterial strains, but nevertheless, a denitrification.

Figure 6. ANAMMOX Bacterium

The question now is: under analogous conditions, can ANAMMOX occur in an aquarium? Obviously we are not able to establish that but we can make some considerations. A driven DSB can reproduce optimum conditions for this process. In fact, nitrogen bubbles are visible in the depths of the sediment. In line with this, it has been experimentally observed (but not in an aquarium) that the higher the layer of sediment, the more pushed the anoxic condition (oxygen inhibits the reaction) and the faster is the reaction. Therefore the high efficiency of a DSB in removing nitrates can be also due to a non-canonical denitrification, besides the classic anaerobic denitrification; obviously, the eventual presence of qualified bacterial strains has yet to be defined. Figure 7 illustrates the schematic diagram of integrated nitrogen cycle with the new reactions and the areas in which they occur.

Figure 7. Nitrogen cycle as revised and integrated. Areas where reactions occur are made evident.

In conclusion, these constant discoveries clarify many obscure points of the nitrogen cycle but at the same time they open up new horizons and paradigms that make these processes even more complex and fascinating. On the other hand, I hope not to have further complicated the well-established ideas on nitrogen cycle, with this article. I also wish that over time, these new discoveries can be applied and integrated with the aquarium, in spite of the scarce scientific researches in this area. However, even if just theoretical, this knowledge allows us to better understand that which can occur in our tanks and nurture our passion for aquarium.

References

1. Arrigo K. R. (2005) Marine microorganisms and global nutrient cycles. Nature 437: 349-355.
2. Berman-Frank I., Lundgren P., & Falkowski P. (2003) Nitrogen fixation and photosynthetic oxygen evolution in cyanobacteria. Res.Microbiol. 154: 157-164.
3. Brandes J. A., Devol A. H., & Deutsch C. (2007) New developments in the marine nitrogen cycle. Chem.Rev. 107: 577-589.
4. Francis C. A., Beman J. M., & Kuypers M. M. (2007) New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation. ISME.J. 1: 19-27.
5. Jetten M. S. (2008) The microbial nitrogen cycle. Environ.Microbiol. 10: 2903-2909.

Acknowledgements

Marco Colasanti aka marcola62 (moderator of Reefitalia forum). A special thanks is owed to the staff of ReefItalia community for their support.

About the Author

MARCO COLASANTI, born in Rome, Italy, September 15, 1962, has a degree in biology and holds a Ph.D. in Neuroscience. He is currently a Full Professor in Cell Biology at the Department of Biology, Faculty of Sciences of the University of Rome, ITALY. Entrusted with holding courses of Cellular Biology and Laboratory of Cellular Biotechnology for the University Degree of Biology. He entered the aquarium hobby with freshwater tanks (1982) and set up his first saltwater tank in 1995. He is currently a Staff Member as a Moderator of ReefItalia, an Italian reef community. Over the last fifteen years, active in the scientific research on Nitric Oxide (NO) pathway in different models and systems, including fish and invertebrates. Co-author of more than 70 publications in international peer-reviewed ISI journals or books.

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AquaTouch offers two of the most rare and expensive fishes for sale

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AquaTouch offers two of the most rare and expensive fishes for sale

By Leonard Ho - last modified May 14, 2011 09:36 AM

If you have $8999.00 and $7999.00 to spare, you can be the proud owner of an ultra rare Liopropoma aberrans and Jeboehlkia gladifer (respectively). No, the prices aren't typos. These fishes are so rare that not only have they never been available for sale in the aquarium trade, but until recently, no photographs of these species even existed!

Both Liopropoma aberrans and Jeboehlkia gladifer are extreme deep water Atlantic species (we're talking 150+ meter / 500+ feet). Both specimens were collected using a deep sea submersible and are being sold on consignment through AquaTouch (Phoenix, AZ, USA).

In March, Reefbuilders blogged about the first ever collected Liopropoma aberrans available to the aquarium industry. This specimen was reportedly destined for Blue Harbor, Japan. The L.aberrans AquaTouch is selling on consignment may be (and is likely) the same specimen.

Jeboehlkia is a monospecific genus, and virtually no information is available about them. This is a small species; $7999.00 buys you no more than an 4cm (1.5in) of fish. It should be noted Fishbase lists Jeboehlkia gladifer as a subtropical species.

The genus Liopropoma is far better documented; These reef basslets are amongst the smallest members of the grouper family and are found throughout both the Pacific and Atlantic. Other species (Swissguards, Cave Basslets, et al.) in this genus are hardy and good candidates for captivity, although they tend to be on the higher end of the price spectrum due to their reclusiveness and deeper-water occurrences. There are several other rare and expensive deep water Liopropoma, most famous of which are L.carmabi (Caribbean) and L.aurora (Hawaii); However, none come close to the rarity and price of L.aberrans. Like Jeboehlkia gladifer, not much information is available on Liopropoma aberrans, but it's a fairly safe bet that the husbandry of L.aberrans is similar to other Liopropoma.

Now the question is: who's crazy passionate enough to be the first to own these species?

AquaTouch also has in stock two specimens of the Caribbean deep water Lipogramma klayi basslets - for the comparatively bargain price of $999.00 each.

Liopropoma aberrans ($8999.00)

Jeboehlkia gladifer ($7999.00)

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Nine potentially new reef species discovered in Bali, Indonesia (with photos)

Nine potentially new reef species discovered in Bali, Indonesia (with photos)

By Leonard Ho - last modified May 15, 2011 11:23 PM

Scientists with Conservation International (including Gerald R Allen) have discovered nine potentially new reef species comprising of eight fishes and one coral species. The new discoveries include a Pseudochromis, a Garden Eel, Cardinalfishes, Blennies, and a new species of Euphyllia sp. (described as a "Bubble coral," but this genus is known to hobbyists as Torch/Hammer corals).

Photos courtesy of Conservation International’s Bali Rapid Assessment Program. Photos by Gerald Allen and Mark Erdmann

The two week survey of 33 reef sites in Bali documented 953 species of reef fish and 397 species of coral. In addition to the new species they discovered, the team of scientists also reported good news pertaining to overall reef health. Ketut Sarjana Putra, the acting Executive Director for Conservation International-Indonesia states, "Compared to twelve years ago, we observed an increase in healthy coral reef cover in the area surveyed, indicating a recovery phase. That is why it needs serious protection and management, to complete the revitalization.

The new fish species have not been named yet, but they were in the genera of Siphamia, Heteroconger, Apogon, Parapercis, Meiacanthus, Manonichthys, Grallenia and Pseudochromis.

More photos and information can be found on Conservation International's website.

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About poison frogs

About poison frogs

Ranitomeya uakarii, a newly-described poison frog species (photo: Jason Brown)

About poison frogs

The poison frogs (families Aromobatidae and Dendrobatidae) are a diverse group of small, diurnal frogs known for their bright coloration, toxicity, and complex parental behaviors. The group contains roughly 250 species occurring from Nicaragua to Bolivia and throughout the Amazon basin as far east as the Atlantic coast of Brazil. Within this range, poison frogs inhabit a wide variety of ecological niches: high-elevation cloud forests (Oophaga arborea), Amazonian lowlands (Ranitomeya ventrimaculata), and dry Andean scrub forest (D. mysteriosus), to name a few. Approximately 1/3 of poison frog species possess potent toxins which they use for defense against predators. Three of these species are known to be fatal to humans. One, Phyllobates terribilis, is used by the Emberá tribe of Colombia for the arming of poison darts used in hunting. This species is so toxic that darts remain lethal for up to three years without losing their ability to kill medium-sized game. Other species exhibit complex parental care. In Oophaga pumilio, females guard eggs until they hatch. Upon hatching, the mother transports each tadpole on her back to a suitable water body such as a bromeliad axil. Though a female may have a half-dozen tadpoles distributed throughout several bromeliads, she will visit each one every few days to deposit an unfertilized egg for her young, which is the only food these tadpoles will eat.

Global Amphibian Extinctions

Amphibians worldwide are going extinct. Multiple factors, such as global climate change, habitat loss, and infectious diseases, are causing an unprecedented loss of diversity. In 1987, the golden toad (Bufo periglenes) was a common sight in the isolated cloud forests of Monteverde, Costa Rica. In 1988, the frogs began to disappear. By 1989, they were gone, and none have been seen since May 15th of that year. Similar extinctions are occurring throughout the genus Atelopus, a widespread group of riparian toads found throughout the highlands of the neotropics. Of the 77 known species of Atelopus, at least 3 are extinct, and 70 are listed as endangered or critically endangered. Despite these declines, new species continue to be found, underscoring the diversity of this genus. Undoubtedly, many species of Atelopus have gone extinct before they were ever discovered. The insidious chytrid fungus (Batrachochytrium dendrobatidis), is a novel pathogen responsible for many of these declines and is quickly spreading throughout most of the world. Habitat loss also threatens many tropical amphibians. Amazonian deforestation is reducing the amount of habitable rainforest by roughly 3.7-4.9 million acres per year (Kricher, A Neotropical Companion).

Poison frog habitat in central Peru (photo: Evan Twomey).

Deforestation not only destroys habitat directly but modifies adjacent habitat by creating hotter, drier conditions than normal. Many poison frogs, which often have small distributions near human settlements, are experiencing drastic reductions in habitat size and quality. Due to their bright colors and interesting behaviors, poison frogs are in high demand in the pet trade. Against CITES regulations, these frogs are frequently smuggled out of their native habitat by the hundreds to be sold in Europe or the US. These practices result in extremely high mortality in smuggled frogs, and in some cases, can substantially degrade natural populations.

Our Goal

This website exists for two primary reasons. The first is to promote the study and conservation of poison frogs by gathering and condensing new and old information and making it available to the general public. Unlike many other poison frog websites, we provide original field accounts, with original photography of wild frogs in hopes to increase awareness and interest of these incredible animals. All our accounts are written by people that have seen and photographed the species in its natural environment. As many of these frogs are at risk due to habitat loss and smuggling, we attempt to provide a summary of the current conservation issues regarding each species. We also summarize the phylogenetic status for each species to emphasize the importance of conserving unique evolutionary lineages.

The second purpose of this website is to provide a platform us to announce recent happenings in the poison frog field. We are a small group of field biologists dedicated to the investigation of poison frog diversity and conservation. Our work focuses on traveling to remote or unknown areas to document poison frog diversity and distribution patterns. On these expeditions, we have expanded the knowledge base of many poorly understood species, rediscovered lost species, and on occasion, we have discovered species previously unknown to science.

Comments or questions regarding this site or our current activities can be directed to Evan Twomey (evan.twomey@gmail.com).

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Introduction and building the Paludarium

Introduction and building the Paludarium

Introduction and building the Paludarium
I will start with a short story about how it all started, me building a wooden tank. At first I must tell you that my hobby is placed in the loft. This is a compromise with my wife who does not want my fussing and tinkering in the living room. I must say, finally the compromise suits me very well and for the following reasons: As we have two little children we decided after the birth of the first one not to smoke in the house, leaving the garden and the loft as smoking areas. During the summer the garden is a perfect choice, but at times when it is cold I prefer to be inside… At second when I am working at my tank and I made a real mess, I can leave things as they are and continue the following day without having to bother about cleaning up the mess I made in all my enthousiasm. In short I am quite pleased with my loft, which is redesigned to a second living room.

Now something about my self. Years ago I started keeping an aquarium This was a cichlid tank with lots of stones in it. My second tank was a South American tak with dwarf cichlids such as Apistogramma. Beneath you see an impression with a picture of the technique which I think comes with our hobby.





And now, let's talk about the new tank.
As I practice my hobby in the loft, of course I see also my fellow hobbyists there. One of these "soul mates" is my friend Rob wich whom I spent many hours in the loft enjoying a cigarette etc. Happily for Rob he stopped smoking, but this does not keep him from - despite my smoking - visiting me to think about and help constructing the new tank. After a while, as long as two and a half years - looking at the old tank, I discovered that there remained quite some space next to the tank to construct a new, bigger tank. This was also because Rob had the idea to construct a tank of his own, with the dimensions 300/90/300 cm! Yes, there is always someone bigger. Now back to the space I wanted to use. First I needed to discuss the subject with my wife, I realized just in time. At the loft we had a walk-in changing room; that had to go of course. But where to put the wardrobe? My wife liked the empty, spacious bedroom and was used to not having a wardrobe around in our bedroom. Very cautiously I started suggesting the enlargement of our bedroom with a dormer. The room will get nice and big, I said. She argreed with me. We could at last place a nice big wardrobe in our bedroom, I quickly added. And it's so cold in the loft, changing your clothes in winter, I said so convincingly as possible…

To keep a long story short, and to continue with the actual story: the dormer was built, the wardrobe was placed and now I have the space of my life. And now let's continue with the paludarium that we are making.

Of course some time went before designing, constructing etcetera. At first I needed to calculate the weight of the complete tank with further structure, water and glass. Soon we realized that there would be a considerable weight, all things put together. The aquarium 250/85/60 cm would contain nett 1275 litre and added to that the structure: 5 plates of plywood for aquarium and top structure, 3 plates of plywood with joists for stengthening etcetera. Het whole contraption had to stand in the loft, so it seemed advised to look at the carrying-capacity of the concrete floor.

Of course you understood already: the concrete floor was not strong enough. Happily there was a wall made of 20 cm concrete. New calculations followed. I was happy that Rob is an engineer en he has the expertise to make calculations for construction of else knows someons who can do that (thanks again, Rob!). We could carry on with the plan, for we had 4 steel consoles especially made. We could build on. The consoles were attached to the wall with special 16 mm bolts wich were chemically fastened 15 cm into the wall. The bottom of the aquarium is now situated 60 cm above the floor, so the consoles are 60 cm high and 95 cm across.

Because it had to become a paludarium I did not want stabilising strips on the glass and I wanted the front panel glazed at three sides, because I did not want to look at a long girder above the water. No, just glass at the front en above that sliding glass panels for the paludarium part. This made a lot of further calculations necessary, for a glass front panel had to resist the total water pressure. Calculations showed that 15 mm float glass should do the trick, or else 10/10/2=2,1 cm layered glass. The aquarium is constructed of wbp or waterproof plywood 18 mm, double layered, so a double layered bottom, back and sides, because it had to be a very firm construction because of the absence of stabilizers in and on the aquarium.

As you can see on the above detailed picture, we have at first made a model to see how the plates could at best be screwed on and to eachother: this was quite a puzzle. So far the first part about the construction and the first batch of pictures. For the remaining part of the construction I shall proceed with the treatment of the wood in order to get a watertight tank and construction. After that we will come to the technique used in and around the aquarium and the paludarium. Eventually the furnishing of the aquarium will be discussed, as well as the furnishing of the paludarium and finally the animals and fishes that will form the population of it all.

So, let's get on with the tank!
The plywood plates en the top structure are glued and screwed together, so the raw construction is ready. The inner corners of the aquarium are treated with a thick layer of epoxy resin, as you can see on the picture.

The meaning of these rounded corners is, that when you apply fibreglass mats, these are not glued squarely tho the wood, but follow smoothly the finished inner corners. After the treatment of the corners, with due observance of the time things need to dry, you can sand the resin and the wood that need further treatment with sanding paper 80.

After that you can apply the first layer or impregnating medium on the treated parts to ensure a good fastening. If you want to go on right away, you can apply the first mat(s) of fibreglass as long as the impregnated layer is still feeling sticky.
For the aquarium part I need 300 gram mats and for the top structure240 gram mats. The fibreglass mat which is applied sticks in some way into the still sticky impregnating layer. Then you saturate the fibreglass mat very well with the epoxy resin and the hardener that goes with it, by use of a fleece roller and a brush. Then roll out with a special metal roller to press out occurring air bubbles. In our case I applied two 300 gram mats for the aquarium on top of each other, of course with some time in between, and a single 240 mat for the top structure. After applying the last mat you need to apply an aftertreatment layer of epoxy resin twice. That is each time when the layer still feels sticky. You can of course let each layer dry completely before continuing with the next, but in that case each layer has to be sanded when dry. Eventually we spent 14 hours on end doing all that with my tank.
The next morning we looked at the result right away of course. The bottom of the tank looked nice an smooth, the walls however had some spots where the fibreglass mat could be pushed in. Yes, laminating is a trade of it's own and some expertise is needed. Expertise which we did not have… How to proceed, was the first that came to my mind. You could inject the spots with air behind them and then fill them with resin. I had to admit that the project with resin and fibreglass mats was nog completely succesful.
This was not caused by the product used, but we simply had not enough expertise with laminating and the use of heavy fibreglass mats. The tank would probably be watertight, but I didn't want to take any risks. In the end I chose to have the inner side of the aquarium covered with 6 mm glass on top of the epoxy layer. This meant extra costs, but I could not take the risk of having to put a bucket here and there below the aquarium. Eventually a nice watertight tank, I hope. I have to fill it yet…

In the meantime the lighting hood got ready. In the hood I placed two electric fans: one to blow air from above across the front window. At the back of the hood three ventilation gratings were placed as you can see on the picture. In this way a good circulation comes into being throughout the vivarium and the lighting hood.

The second fan is meant to - whenever desired - suck heat and moisture out of the lighting hood. My advantage is, that I already had a chimney shaft at my loft, to which I connected the fan. This makes it possible to cool the tank faster to approximately 20/21 degrees Celsius at nightfall, when the lights dim. Also during the summer with warm days it is possible to suck out warm air from the tank and hood and to get it outside through te shaft.
The two fans have regulated r.p.m., and I have to find out by trial and error which is the best setting and which are the best intervals for the second fan, which is regulated by a timer. The lighting hood is fitted with two high pressure natrium lamps of 110 watts each. These lamps are tested in several vivaria and are treated extensively in the book "Bromelien, Orchideeen und Tropenterrarium" by Benjamin & Wolfgang Swarz. The great advantage of those lamps is, that the emit relatively low heat and as such can be used very well al lighting in al lighting hood without causing to high temperatures in the hood.

Beside this 6 fluorescent lamps were fitted: 2 of 54 watts and 4 of 18 watts which are electronically regulated. Above these lamps reflectors were placed to let the light shine where I want it to. Furthermore I fitted two halogene spotlights of 50 watts each which provide local lighting. I will have to find out which intervals I have to use for these lamps. And then there is a E 27 lamp of 7 watts for the night, to create some dim light at night. To partition off the lighting hood from the paludarium I used polycarbonate panels with reflector grids above. For now we take a break, to continue afterwards with the decoration within the paludarium.

And further we go with the inner tank
and the materials used.
First the system of conduit-pipes. As you can see on the pictures I made two overflow passages for the overflow of the aquarium to the biological filter. These overflows are about 4 cm wide and join outside the tank in a shared pipe that runs to just above my biological filter at the outside of the aquarium.


I can clean the overflow whenever needed by use of a screwed cap on the pvc. For hard pvc there were created 6 passages for the circulation of the water and for the current of the waterfalls. In the top structure I created two waterfalls which are circulated by a canister filter. At the pressure side of the pump I made a distributor with three outlets at the outside of the aquarium.

One for the first waterfall, the second for the second waterfall and a third for the remaining water. On each outlet I mounted a tap, for me to control each current. The third tap is for the remaining water with an outlet at the bottom of the aquarium, where I would expect still water. Controlling the two taps for the waterfalls, the remaining capacity of the pump (1250 litres p/h at zero delivery head) can get rid of its surplus water..


At the right side of the aquarium an outlet of a delivery pump (2200 litres p/h) is located. This pump pumps up the water from my biological filter back into the aquarium. At the right back side another outlet of a pump (1250 litres p/h with zero delivery head) is located. This pump sends water to my PH-electrode and temparaturesensor. As there is a contiuous flow of water along these measurement points I can always measure the right values. This pump also serves my reactor for the CO2 that I use to control my PH. On this pump I made a bypass, so when I have a problem or should do some work in the aquarium, I don't have to shut down the circulation; my biological filter can continue circulating. For the further furnishing of the top structure and the inner part of the aquarium I applied polystyrene and polyurethane foam.

After at first glueing and "foaming" the raw contours follows the finishing and modeling of rocks, under water landscaping and the bank, to let the bank continue to the top eventually. I used a lot of tropical hardwood roots which I attached into the back wall. I would not have done this with bog wood. The hardwood will last for a long time before starting to rot. We used a gass torch too, to add some relief. When all was modeled to my liking, I treated the whole with epoxy resin, mixed with hardener and pigments. For the top structure I used the colour dark brown. You apply the resin on a part, after which you sprinkle peat (dust) which you pat into the resin. In total you will be busy with the top structure an entire week: first you let the part that you treated get dry and the next day you proceed. Below the waterline the epoxy resin is mixed with the pigments ochre and brown. This you brush on the polystyrene, sprinkle it with sand and pat it in again. Just look at the pictures for the result. All conduits are hidden behind the polyurethane foam and the polystyrene. I kept the curved joints as wide as possible to clean the conduits at a later moment when needed. All conduits are across 20 mm with wide curved joints of hard pvc.




For the photo reportage I want to give a big compliment to David, who documented it all in a great way. I thank everyone who helped me to complete this project.

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Terrarium

Terrarium

y Will K. - 2007-12-10

Terrarium making is a rewarding hobby that combines art and nature. You can make a nice terrarium in an hour and then enjoy caring for it and looking at it for years to come.

* * *

With a few tips and guidelines you can make some wonderful terrariums that are extraordinary.

A vivarium is an area, usually enclosed, for keeping and raising animals or plants for observation or research. A vivarium may be small enough to sit on a desk or table, such as a terrarium or an aquarium, or may be a very large structure, possibly outdoors.

What is a terrarium?

A terrarium is a small environment where plants and sometimes animals live together in their own little environment. Generally, this environment ranges in size from that of a two-liter bottle of soda to a thirty-gallon fish tank.

There are two basic types of terrariums: closed environment and open environment.

In a closed environment the terrarium is sealed and it is an ecosystem unto itself that needs very little except occasional watering and moderate sunlight.

An open environment terrarium is more common and is usually one where the top is open. This type of terrarium is more durable and easier to maintain. I recommend that you make an open top terrarium if this is your first attempt at making a terrarium.

The Basics:

Enclosure selection: The most important decision you make when making a terrarium is choosing what type of container to put it in. This container has a dramatic impact on how the terrarium looks so you should choose something that looks nice. Some common choices include large brandy glasses, large bottles, fish tanks or even ceramic bowls.

Theme: The best terrariums are the ones that go a little bit further than just a group of plants. Consider making your terrarium with a theme and then you can add little extras that add excitement to it. Some good theme ideas include a desert theme, a rainforest theme, or a magical theme that might include small statues or figurines.

Plant Selection: Most types of houseplants are suitable for a terrarium. But you should consider a couple of things. Make sure you use plants that will not grow too large. These plants will overshadow other plants. And use a variety of colors, heights, and leaf shapes in your terrarium. This will make it more pleasing to the eye. Finally, you may want to follow the odd number rule and place 3, 5, or 7 plants in the terrarium. Odd numbers of plants tend to make more pleasing arrangements. It looks more natural.

Buying Plants: When buying your plants you should try to buy plants with similar sunlight and watering needs. Read the labels or tags on the plants. A good selection of plants would be ones that all have the recommendation of moderate sunlight and watering. Being all in the same environment it would be difficult to give the different plants varying amounts of sunlight and water.

Arranging the Plants: Before you plant the plants into your terrarium you should decide how they would be arranged. Place the plants in their pots side by side and move them around to look for interesting arrangements. Think of what a florist does when he makes a floral arrangement. If the pots themselves don't allow you to get the plants into a good arrangement you can take the plants right out of their pots with their root systems still in the soil and try arranging them on a large dish. Once you have found an arrangement that looks good you can then transfer the plants right into the terrarium.

How to build the terrarium:

1. Clean the terrarium container with a mild soapy water and rinse it thoroughly to remove any soap residue

2. Place a thin layer of pebbles or small stones in the bottom of the terrarium (this helps with drainage and water management)

3. Place a thin layer of activated charcoal over the pebbles - If you are making a closed environment terrarium you should do this step. The charcoal will keep the water clean. If you are making an open terrarium you can skip this step.

4. Place a thin layer of spaghnum or Spanish moss on top of charcoal or pebbles. This will act as a bedding material that will keep separation between the soil and the pebbles. Without this moss the soil will settle down into the pebbles and get muddy.

5. Place a thick layer of your potting soil on top.

6. Plant your plants into the soil.

7. Place all your extra materials and create your theme - this can make your terrarium much more attractive. Use things like small trinkets, statues, or colorful rocks. A unicorn, dragon or fairy would make a perfect addition to a terrarium.

Care of your terrarium

A terrarium can be very hardy and you should follow the general rules of indoor plants by giving it moderate amounts of water and sunlight. If you have made a closed environment terrarium it is possible to go weeks without ever having to water it. The water will pull up from the rocks and form a mist on the top of the terrarium then drip back down and water the plants. This closed loop system is very similar to what happens in the real world.

A terrarium is a beautiful composition of plants and flowers that require only minimum care. If you follow some of the basic rules of terrarium making and you add some creative touches you will have something that you can show off to your friends and that you can enjoy for years to come.

If you would like to learn more about making terrariums including how to make the ultimate terrarium complete with a waterfall and underground cavern for your pet, visit the authors terrarium website

Read more: http://www.disabled-world.com/artman/publish/terrarium.shtml#ixzz1MWrYrg9l

Glass terrariums: The retro trend is back to stay!

Shikha Chauhan | Jun 29 2010

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Terrariums or call them mini gardens, they are just the new way to create miniature greenhouse in a very small space. Terrariums are a wonderful way to bring the outdoors right inside the house. They are the new definition of bringing artwork and living things all at once. They are nothing more than an independent ecosystem under glass or put in better words as a garden in a bottle that are easy to maintain. The delicacy and charisma of the miniature gardens not only gets us close to nature, but also creates a restful mood.

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Aquarium Fish: A Look at the Gobies

Aquarium Fish: A Look at the Gobies

By James W. Fatherree, M.Sc.

After all, many (but certainly not all) are quite hardy and easy to care for, and many are attractive and/or have interesting behaviors. This is especially so when it comes to some of my personal favorites, the shrimp gobies.

Comments

Contents

1. The Sifter Gobies
2. The Dragon Goby:
3. The Rainford's Goby:
4. The Neon Gobies:
5. The Clown Gobies
6. The Catalina Goby
7. The Shrimp Gobies:
8. A bit about the shrimps:
9. References:

Despite the typically small size of its members, the family Gobiidae is the largest family of marine fishes, being the home of over 2,000 species. Of course, I won't be going over all of these, but I do want to give you an introduction to the family and cover some of the species most commonly seen in the hobby. After all, many (but certainly not all) are quite hardy and easy to care for, and many are attractive and/or have interesting behaviors. This is especially so when it comes to some of my personal favorites, the shrimp gobies.

Before getting into any specifics, I'll say that essentially all gobies live on or very near the bottom. So, you won't likely see one swimming around in the upper parts of your aquarium too often, unless their after some food. The vast majority also stay relatively small, as in less than four inches in length. Thus, many can make great additions to smaller aquariums, but their diminutive size may make them less appealing to some hobbyists, as they can easily be "lost" in large aquariums. Small gobies can also become expensive snacks for any larger predatory fishes in a tank, so they should probably be left out of any aquarium housing any such fishes, too. They're also prone to jumping out of tanks if they are harassed or spooked, so a glass top is a good idea, as well. But, there isn't much else of interest to say here though, as there are so many different types of gobies that it's difficult to make general statements about them. Many are sand sifters, some are cleaners, a few live with burrowing shrimps, etc. So, it's time to take a closer look...

The Sifter Gobies

When it comes to gobies, the sifters (also commonly called sleepers for some reason) can get relatively large, with some species reaching 6 or 7 inches in length. They're generally quite peaceful with other sorts of fishes though, so don't be worried about their size. They're also a hardy bunch and can be quite useful at times, too.

They feed on tiny sand-dwelling invertebrates, and collect them by scooping up mouthfuls of sand, which is also why they're often called sifters. They'll essentially make a shallow nose dive into sandy substrates, fill their mouth with sand, and then quickly sift through it in order to capture any edible organisms within it. The sorted sand is ejected through the gill slits behind the head, and then they'll take another scoop.

This feeding activity can help to keep the upper layer of a sand bed cleaner, but you should note that if you're trying to maintain a thriving deep sand bed, these fishes will indeed eat some of the beneficial organisms living in it. I've found that they don't really deplete a sand bed of critters if kept in a large enough system housing enough sand, but they can literally clean out a relatively shallow sand bed in a smaller aquarium.

Again, they usually get along fine with other types of fishes, but they may not get along so well with other species of sifters or other individuals of the same species, either. So, it's best to keep just one in a tank, or a mated pair, unless the tank is large and has plenty of room for everyone. They'll typically learn to take a variety of fish foods too, although some hobbyists have reported otherwise on occasion. I've had no problems keeping the two most common species Valenciennea puellaris and V. strigata, but can't say much for the others.

Sifter gobies feed by gulping sand and sorting out any small, edible invertebrates.

Valenciennea puellaris">

The orange-spotted sleeper/sifter goby, Valenciennea puellaris

Valenciennea strigata.">

The yellow-headed sleeper/sifter goby, Valenciennea strigata.

The Dragon Goby:

The dragon goby (or brownbarred goby, Amblygobius phalaena) is another one that can get big for a goby, sometimes reaching lengths of about 6 inches. This is another a sifter that also scoops up mouthfuls of sand and consumes the creatures living in it, and can thus help keep a sand bed clean, too.

Like the above, they should be kept one to a tank, although they're more likely to get along okay with other sorts of fishes, including other types of sifters, again as long as there's plenty of room for everyone. But, that's not always the case, as they never get along with other dragon gobies best as I can tell, unless they're kept as a mated pair.

Amblygobius phalaena.">

The dragon goby, Amblygobius phalaena.

The Rainford's Goby:

The Rainford's goby (or Old Glory goby, Amblygobius rainfordi), is a beautiful little fish, typically staying under 2.5 inches, but they're especially prone to die from starvation. I've also been told that they don't ship well, either. I've never tried keeping one myself due to the fact that everything I've heard/read about them indicates that they need to graze on green filamentous algae (hair algae) in order to thrive, or even survive. Hair algae is usually something that reef aquarists should try to avoid like the plague, so I think it's safe to say that this fish is a no-go for reef aquariums. Admittedly, I have read one report of a hobbyist that through persistence was able to get one to eat a few types of fish food (Michael, 2005). But, that's just one report.

Still, if you're into taking risks with the lives of fishes, note that these should be kept one per tank, or as mated pairs. However, with that said, Michael (2005) also reported that they usually occur singly, not in pairs, in the wild, and that he purchased a supposed mated pair that didn't get along at all. Just pick something else folks…

Amblygobius rainfordi.">

The Rainford's goby, Amblygobius rainfordi.

The Neon Gobies:

These predominantly Caribbean species are some of the smallest, staying under two inches, and are generally quite hardy "cleaners" that help keep other fishes at their best. Like the cleaner wrasses, these gobies will eat any parasites or dead skin they can find on another fish, which is why they're all called cleaners.

In the wild they tend to sit around at a "cleaning station", which may be operated by a single neon goby, but more often they're seen hanging around in pairs or in small groups where other fishes know to come for a good going over. These fishes looking for a cleaning recognize the neon gobies for what they are and refrain from harassing or eating them, and the gobies can get a meal out of the deal, of course.

These are far better choices than the cleaner wrasses though, because the wrasses oftentimes will not take any sort of fish foods offered and often end up starving to death in aquariums. To the contrary, the neon gobies will typically eat a variety of fish foods and can be kept with or without other fishes. So, they'll clean if they can, but won't starve if they can't.

Gobiosoma. There are several species, but many of these look so similar that I won't attempt a species-level identification.">

Two neon gobies of the genus Gobiosoma. There are several species, but many of these look so similar that I won't attempt a species-level identification.

The Clown Gobies

The clown gobies (or coral gobies) are also quite small, staying under 2.5 inches in length. In fact, the most common species (Gobiodon okinawae) doesn't even reach 1.5 inches, making them well-suited for life in very small tanks. They're brightly colored too, and typically won't bother anyone with the exception of other clown gobies.

Even though they don't get along well with other clown gobies when kept in confined quarters, if a number of them are kept in a large enough tank with plenty of rock and corals, they'll often pair up into male-female couples and will get along well from there. They also have an odd hangout, as they like to perch in the branches of stony corals like Acropora, but they don't do any harm to them.

About the only other thing to throw in is that they tend to be quite hardy and will eat a wide variety of fish foods, as long as the size is small enough. However, due to their smallness, it's obviously best to keep them with other small, peaceful fishes. Otherwise, they may be harassed by larger tankmates, and more aggressive fishes also tend to get all the food.

Gobiodon okinawae.">

The clown goby, Gobiodon okinawae.

The Catalina Goby

Next is the Catalina goby (or blue-banded goby, Lythrypnus dalli) that hails from the waters off California and Baja Mexico, which is a problem for most of us. This is because these waters are much cooler than our reef aquariums, and even many non-reef marine aquariums. So, our tanks tend to be too warm for these gobies to live in, as they should be kept in the 50's to 60's Fahrenheit and shouldn't be kept at temperatures above the low 70's. I have heard reports of some hobbyists being able to keep them alive at higher temperatures, but I can't help but think they cannot be as healthy or live as long under such conditions. Sorry, but these are unsuitable choices for most us, despite their appearance and availability.

Still, if you have a relatively cool tank, this is another particularly small species (also typically less than two inches length), and several can be kept in one tank. They're actually territorial, but due to their diminutive size, even a 30 gallon tank can be considered plenty big enough to keep a few of them. Of course, you do have think about the other fishes in the tank, which will certainly be larger, and make sure that there's nothing that will harass these gobies. Oh, and they're typically easy to care for, as they'll take a variety of regular fish foods without issue.

Lythrypnus dalli.">

The Catalina goby, Lythrypnus dalli.

The Shrimp Gobies:

The shrimp gobies (which belong to the genus Amblyeleotris, Cryptocentrus, or Stonogobiops) are also rather small in size, and they all live in close relationships with a number of pistol shrimps. These different animals help each other stay alive and well though, as the gobies have great eyesight, while the shrimps have very poor eyesight, but are excellent diggers. In fact, the shrimps can build and maintain burrows in sandy bottoms that are big enough for themselves and for one or more gobies, too. So, the basis of the relationship is that the goby watches out for any potential predators that come too close to the burrow or the shrimp, and will warn the shrimp that trouble is near, while the shrimp makes a home for both of them. I'll tell you more about this below, but for now I do need to point out that these fishes can be kept without shrimps, too.

Stonogobiops yasha, usually pairs up with Alpheus randalli.">

The white-ray shrimp, Stonogobiops yasha, usually pairs up with Alpheus randalli.

Stonogobiops dracula,usually pairs up with Alpheus randalli.">

The Dracula shrimp goby, Stonogobiops dracula,usually pairs up with Alpheus randalli.

Amblyeleotris aurora, usually pairs up with Alpheus randalli.">

The aurora shrimp goby, Amblyeleotris aurora, usually pairs up with Alpheus randalli.

Amblyeleotris randalli, usually pairs up with Alpheus randalli.">

The Randall's shrimp goby, Amblyeleotris randalli, usually pairs up with Alpheus randalli.

Amblyeleotris guttata, usually pairs up with Alpheus ochrostriatus.">

The orange spotted shrimp goby, Amblyeleotris guttata, usually pairs up with Alpheus ochrostriatus.

Cryptocentrus cinctus, isn't always yellow, as they sometimes have dark coloration.">

The yellow watchman goby, Cryptocentrus cinctus, isn't always yellow, as they sometimes have dark coloration.

Stonogobiops nematodes) and a pair of scissortail dartfishes (Ptereleotris evides), which are not gobies, sharing a burrow with two tiger pistol shrimp (Alpheus bellulus). This goby most often pairs up with Alpheus randalli, though.">

Here's a black-ray shrimp goby (Stonogobiops nematodes) and a pair of scissortail dartfishes (Ptereleotris evides), which are not gobies, sharing a burrow with two tiger pistol shrimp (Alpheus bellulus). This goby most often pairs up with Alpheus randalli, though.

Anyway, when they're kept with a shrimp, what you'll see is that the goby is usually out of the burrow, at least partially, but near its entrance, with the shrimp behind it. Sometimes the shrimp will venture out from the goby a few inches at the most while it's working on the burrow, but most of the time it stays close by and maintains physical contact with the goby by touching it with one of its antennae. In the event that the goby feels the need to warn the shrimp of any impending trouble, it'll wiggle its tail or body in a way that alerts the shrimp, and off it goes into the burrow with the goby typically following right behind.

They'll do this if a potential predator comes too close, but they'll oftentimes scram even when harmless fishes get too close at feeding time, or the goby will do just the opposite depending on the competition. I've got a goby/shrimp pair in my 125 gallon, and another in my 55 gallon, and neither of the gobies is a chicken. I've had others that were, though. I'll explain…

Cryptocentrus cinctus) and my tiger pistol shrimp (Alpheus bellulus). This species often pairs with Alpheus djeddensis or A. ochrostriatus, though.">

Here's the pair in my 125, a yellow watchman goby (Cryptocentrus cinctus) and my tiger pistol shrimp (Alpheus bellulus). This species often pairs with Alpheus djeddensis or A. ochrostriatus, though.

Stonogobiops nematodes) and my Randall's pistol shrimp (Alpheus randalli) the most commonly offered species.">

Here's the pair in my 55, a black-ray shrimp goby (Stonogobiops nematodes) and my Randall's pistol shrimp (Alpheus randalli) the most commonly offered species.

The gobies will both eat anything I put in the tank for fishes, but I've been feeding the shrimps with sinking food pellets for over a year now by using a long piece of rigid airline tubing to drop the pellets right into the burrows opening. Still, when my other fishes smell the pellets they go after them, too. Of course, they aren't after the gobies or the shrimps, but the gobies still send the shrimps scurrying away into the burrow. Then, in both tanks, the gobies will chase off the other fishes in an effort to protect the food pellets. They'll open their mouth as wide as possible and charge at the other fishes to fend them off.

My yellow watchman is not to be messed with at feeding time. Here it is chasing off my coral beauty angel.

Despite their going after other fishes trying for their companions' food, none of these gobies really cause any problems with other types of fishes. For the most part they ignore everyone else and mind their own business. Besides, most of these species get no bigger than three to five inches, and are rather skinny. So, they wouldn't pose much of a threat to anything but the smallest of fishes, anyway.

Unfortunately, the exception here is that some species don't care for other gobies, or other individuals of the same species in particular. While there are some that will actually share a burrow with other gobies of the same or other species, there are some that simply will not tolerate having another shrimp goby in the tank with them. These unsocial species will often go after each other relentlessly, until one is finally convinced to hide all time, or is literally run to death. However, there is an exception to the exception, as you may be lucky enough to come across a mated pair for sale, which should get along fine regardless of the species.

Anyway, back to burrows. While you may only see one or two small entrances to a burrow, they're actually much larger than you might expect. At first I wondered how they managed to keep such structures open in a bed of fine sand, but quickly realized that they're quite good at using little bits and pieces of coral rubble, shell, rock, etc. to reinforce the roof and sides of the burrow. They can stack and arrange all sorts of things in ways that give some permanence to the burrows, and constantly work to keep them in good shape.

With this in mind, it's essential to supply some rubble for a shrimp by placing a pile of such stuff near a burrow's entrance. I've provided them with the shells of deceased snails, a good amount of manually broken up pieces of clam shell from the beach, some small pieces (an inch or two) of coral skeleton of various shapes, and similarly sized bits of rock, and they sort through everything for use like a contractor building a stone fence would. Usually, surprisingly quickly, anything I put near a burrow is used somewhere out of sight never to be seen again, and I've provided a heck of a lot of material for them.

I have provided both of my shrimps with large quantities of crushed up clam shell, which they've readily used to support their burrows.

Still, at night the burrows' entrances usually cave in or are closed with the goby and shrimp safely inside. Then, when the lights come on, the shrimps quickly get back to work. They'll dig tirelessly during the day, moving sand around from place to place to clean out and re-open the entrances, and will usually keep it open until the lights go off again. In fact, they stay so busy that it seems as if they actually enjoy the work. They're fun to watch for sure, and I'd say that out of all the things in my aquariums, I spend more time watching the activities of my gobies and shrimps than anything else in the tanks.

If this sounds like something you'd enjoy too, do keep in mind that the gobies typically pair with only certain species of shrimp. So, you'll need to do some further homework before buying anything to make sure you get the right kinds together. If you look around enough, you may be able to buy them together though, which is what I had the good fortune to do in both cases. I'll also throw in that as far as marine fishes go, many gobies are being reared in captivity, and there are numerous such specimens available to us. So, if possible, shop for these in particular.

And that's your look at the gobies.

A bit about the shrimps:

These shrimps all belong the genus Alpheus, and are called pistol or snapping shrimps because they have a specially modified claw that they can use to make a little popping sound with. Not all of these associate with shrimp gobies, though. Some live alone and can get relatively large, and can make a pop that sounds pretty loud. In fact, I used to have one in a non-reef tank that was so loud I could hear it at night in my bedroom, even though the tank was in the den. It had to go. To the contrary, the species that pair up with gobies are all relatively small, and aren't so loud. In fact, I never hear my own shrimp making any noise at all. Why do they do it at all? Well, for the species that can really pop, this is a means of defense, as they try to scare away anything that gets too close by repeatedly popping their claw.

References:

1. Aquacultured Gobies: http://www.orafarm.com/gobies.html
2. Gobiidae.com: http://www.gobiidae.com/
3. Karplus, I. 1987. The association between gobiid fishes and burrowing alpheid shrimps. Oceanography and Marine Biology, Annual Revue, 25: 507-562.
4. Michael, S. 2005. Aquarium Fish: Gobies of the Genus Amblygobius. Advanced Aquarist's Online Magazine: http://www.advancedaquarist.com/2005/3/fish
5. Michael, S.W. 2001. Marine Fishes: 500+ Essential-to-Know Aquarium Species. T.F.H. Publications, Neptune City, NJ. 448pp.
6. Schultz, H.C. 2004. You May Call Me 'Yasha', King of the Stonogobiops. Reefkeeping, 2(12): http://www.reefkeeping.com/issues/2004-01/hcs3/index.php
7. The Shrimp Goby Chronicles: http://www.explorebiodiversity.com/Hawaii/Shrimp-goby/general/index.htm
8. WetWebMedia: http://www.wetwebmedia.com/gobies.htm
9. Wikipedia: http://en.wikipedia.org/wiki/Gobiidae

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