Shadowraven
Aquarium Advice FINatic
Alright folks, as promised, I did further research on the actual toxicity of hydrogen sulfide on aquarium fish. I believe that I have located the information that should lay this case to rest. From several scientific papers and abstracts on the subject here is what I found.
Hydrogen sulfide (hereafter referred to as H2S) is neutralized when it comes in contact with oxygenated water, with a few caveats. The effect the water will have depends on the amount of oxygen dissolved in the water and the concentration or amount of the H2S present. H2S is also slightly soluble in water forming a weak acid.
In low concentrations H2S is harmless. All animals produce some as a byproduct of the metabolization of nutrients. Animals even need small amounts of it to be present for some biological processes to occur. The body detoxifies the H2S present into less toxic sulfates. These resultant sulfates are then excreted in the urine. Hence in small concentrations, H2S exposure can occur indefinitely without any side effects. At some point a threshold is reached where the body’s ability to oxidize the H2S becomes overwhelmed. The H2S reacts with alkalis in the body to form the caustic, sodium sulfide. When enough of it is present, it forms a bond with iron in the body that prevents cellular respiration. In humans the inhalation of amyl nitrite and/or pure oxygen is necessary to affect a cure. In higher concentrations a single breath results in death.
When small amounts of H2S contacts oxygenated water it oxidizes into sulfates which are much less toxic. Higher concentration of H2S can overwhelm the oxygenated water and become toxic to anything living in it. Most of the time this won’t occur in a well-maintained aquarium, as there is plentiful oxygen dissolved in the water and very little H2S gas present. But if the oxygen is low, or the amount of H2S high, it is lethal to everything in the tank.
That is why it appears to be such a rare event with aquaria. Most of us keep decent enough care of our tanks to keep this from ever happening. It is a great example of the importance of keeping your substrate clean, mixed and well oxygenated.
In conclusion we can see that while this is a very rare occurrence, it isn’t a myth, it can happen.
Primary Sources:
term+@rn+@rel+7783-06-4http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=402&loc=ec_rcs
There are secondary sources, but they are very numerous.
