My main question is how many water changes can I do without affecting the healthy bacteria? I recently had an algae bloom in my fish tank and went to petco for information on how to get rid of it and they gave me AlgaeGone by Topfin. After buying it I began treatments didn't notice any changes till I came home on friday and found a dead red tailed shark and a dead platy and found a slimy white filament covering a good portion of my tank. I immediately siphoned out as much as I could but ended up doing almost a 40% water change because of the amount of water I siphoned. My other fish seemed to be doing ok until today when I found another dead platy and noticed some others nipping the white fliamnets. I wan't to siphon more out but don't want to mess up the cycle of the tank. Not sure what to do and I don't really trust petco. Any tips? I have a 38 gallon tank currently 5 platys 3 red paradise gouramis 2 rose-barbs and a rainbow shark and 2.5x filtration.