The clowfish and the diamond goby
Recently, the SSMV aquarium has encountered some challenges with its biotic and abiotic conditions, so we thought we would use this post to let you know about the lessons we have learned. First, our beloved Sally Lightfoot crab died (see our video about the life and death of this crab here: https://www.youtube.com/watch?v=XH9TKkfnFWE). We are not sure of the exact cause of death, but one hypothesis is that the crab lost a fight, of which it was the instigator. The Sally Lightfoot crab had a history of attacking other marine life in the aquarium, such as mollusks, shrimp, serpent stars and clownfish. We also found a hole in the crab’s lower abdomen, which is not in the anatomy of a Sally Lightfoot crab.
We have overcome a pH issue in our aquarium. pH stands for the potential of hydrogen and is simply “a logarithmic measure of the concentration of hydronium ions in a solution .” A hydronium ion, also called an oxonium ion, has three hydrogens and 1 oxygen. It forms when an acid dissociates into water . An acid is a compound that donates a proton. On the other hand, a hydroxide ion is composed of an Oxygen and a Hydrogen and is usually conceived with the dissociation of a base . A solution that is more acidic has a greater concentration of hydronium ions relative to hydroxide ions. On the other hand, a more basic solution has a greater concentration of hydroxide ions relative to hydronium ions. Our saltwater animals typically need a pH of 8.1-8.4 (i.e. slightly basic water), and fish can die if the pH falls to around 7.2-7.4. Lower than ideal pH can interfere with a fish’ ability to take in water through its gills.
Part of this issue may be related to high carbon dioxide levels. When Carbon Dioxide enters water, it forms carbonic acid. Since carbonic acid is a weak acid, it dissociates into hydrogen ions and bicarbonate ions. In addition, a reduction in the availability of carbonate ions (a problem that is exacerbated by existing carbonate in the water bonding with the hydrogen ions) affects marine life such as corals as they are unable to absorb the calcium carbonate that they need to survive, i.e., to keep a healthy skeleton. This in turn affects the rest of the ecosystem that needs a healthy reef to survive . A lower pH may also affect their sense of smell and the Carbon Dioxide that triggers ocean acidification impairs the growth of the otolith, which assists the clownfish in sensing motion and in staying upright . Additionally, ocean acidification affects plankton, which we use in our aquarium for feeding. Plankton such as pteropods are not able to build their shells. In recent years, such pteropods in the Pacific Northwest have been found to have their shells totally dissolved .
Moreover, our tank is in a basement, which leads to less fresh air. All animals (both aquatic and non-aquatic ones) undergo respiration, a product of which is carbon dioxide. A quick buildup of Carbon Dioxide in the water could be due, in part to a lack of seaweed. Since plants/seaweed undergo photosynthesis, producing oxygen, Carbon Dioxide buildup, and its effects on pH can be tackled by adding seaweeds and other algae, which includes free-living phytoplankton and the zooxanthellae in the coral tissues, also respire when the lights are turned off at night in the aquarium. Hence the high fish mortality rates at night. Moreover, we have a hypothesis that the clownfish has been attacking other fish which we will address in another post. Zooxanthellae are photosynthetic algae (dinoflagellates) that have a mutualistic relationship with the corals . The zooxanthellae provides the corals with oxygen, energy, and organic materials that are required for photosynthesis. The corals provide the zooxanthellae with light, protection, carbon dioxide, nitrogen, and phosphorous which allows the zooxanthellae to undergo photosynthesis [6,7]. Furthermore, the zooxanthellae provides corals with colors other than white. When the zooxanthellae are stressed, coral bleaching (whitening of the color and ultimately death) occurs as the zooxanthellae leave the corals. 
Furthermore, alkalinity levels that were slightly lower than needed. Alkalinity is the ability of water to resist acidification .
Some solutions that we have employed are, first, adding macroalgae to the refugium, which provides additional oxygen through photosynthesis. Second, we set up nocturnal lighting in the sump, to allow the macroalgae to photosynthesise and remove CO2 at night too. Three, we have been adding calcium and carbonate supplements to increase alkalinity and in turn, pH. This works because these compounds lower the concentration of Hydrogen ions by combining the hydroxide ions and in turn increases the pH by lowering the acidity . We set up an automatic dosing system to release 20 ml of these supplements into the main tank every day (5 ml at four separate times of the day). Every day we test the alkalinity and pH of the water using test strips from PetSmart. Besides alkalinity and pH, these strips measure nitrate, nitrite and chlorine levels, as well as water hardness, all of which need to be monitored because they also have the potential to adversely affect our organisms.
We have also switched from using deionised water for our water top-ups (water needs to be topped up in the aquarium to cover losses from evaporation), to using reverse osmosis water. Reverse osmosis water contains less impurities than deionised water. This is because deionised water is water with only ions removed . Reverse Osmosis water is more pure as water goes from a less pure solution to a more pure solution . Reverse osmosis systems remove almost all the impurities from the water. They work by using pressure to force water (e.g. from your household faucet) through a membrane. Only the smallest particles can pass through this membrane, whilst larger ones like heavy metals and cysts can’t. Hence impurities are removed and the water is “cleaned”.
Looking ahead, we are always looking to add more marine life such as larger fish. As of now, the SSMV instructors are looking into having the freshman do a spring semester project with the aquarium. Furthermore, we are also considering adding a quarantine tank as the clownfish may be ready to mate. If you would like to help us make a difference, please consider doing one or more of the following:
Following us on Facebook: https://www.facebook.com/SSMVAquarium
Following us on Twitter: https://twitter.com/SSMVAquarium
Donating via our GoFundMe page: https://www.gofundme.com/ssmv-aquarium-maintenance-funds
Staying tuned to this blog!
Until next time:
SSMV aquarium blog
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 T. Mondal, C. Raghunathan, & K. Venkataraman. (2014, Oct.). “Coral Bleaching in Andaman Sea–And Indicator for Climate Change in Andaman and Nicobar Islands.” Indian Journal of of Geo-Marine Sciences. [Online]. Vol 43. (10), pp. 1945-1948. Available: http://nopr.niscair.res.in/bitstream/123456789/34549/1/IJMS%2043%2810%29%201945-1948.pdf
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 National Oceanic and Atmospheric Association, “Corals”, [Online]. Available: https://oceanservice.noaa.gov/education/tutorial_corals/coral02_zooxanthellae.html