I don't have much time, but do you quarantine? Have you asked the lfs
' to see what medications they use on their fish and which ones they keep in constant circulation? Your temperature and salinity are fine, but do try and regulate the temp. a little more with a fan. Are the fish intact when you find them? How are the other fish reacting (breathing, behaviors, etc). when one is dieing? Have you tested the water parameters early in the am, around 3-4am for significant changes (DO, pH, etc.)? Does the cat pursue your animals or have you checked in early am for a predator (internal)?