In a mature tank or (cycled) tank ,with healthy biological filter (beneficial bacteria, see cycling ) and proper tank maint (IE) weekly water changes and test results that yeild zero ammonia,zero nitrites,and nitrAtes of twenty or below,, along with temp above 74 degrees,, There are few common diseases. If water quality begins to suffer for some reason then there are any number of pathogens which can affect the weakend fish. When in doubt,, I perform daily ten to twenty percent water changes using a good dechlorinator for new water before itr goes in the tank. |