|MadSci Network: Environment & Ecology|
I have to admit that I didn't know where to begin with this one, so I asked the resident expert in our laboratory, Bruce Woodin. This man not only knows his fish physiology, but also worked in an aquarium shop while in school. This was his answer: Teleosts primarily excrete ammonia (not urea), which is toxic, but generally not a problem after dilution in an open system. In a closed system (aquarium), bacteria utilize the ammonia to synthesize amino acids and thus eliminate it from the aqurium water in an established tank. The reversible reactions involved require 2 protons, which become limiting in an alkaline environment (favoring ammonia remaining as such).
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