Dont over feed.I found out a formule.Dont feed when the fish only have a tiny bit of fed meter down.I feed when the have a quareter of there fed down.This way they lose no health when fed.On the other hand if there fed meter gets too low they lose health,but thats ,like,below half way and as long as you follow my feeding pattern your fish should stay healthy.It is very confuseing.I killed a whole tank like this when i first started.Hope this helps some noobies