Ok i started a 55 gal on 3-12-12. Bio Boost vitamins Aquar Clear 110 all added same day. On 3-26-12 i Went to walmart and found a Pictus Cat that i kind of impulsed bought and decided to add 4 mollies with him as starter fish while the tank cycled. Added them They all seem to be good except for one mollie was a little weird at first but then seem to come around. The pictus cat acted great really quick around the tank, started to like him a lot. Was feeding him blood worms. I bought a Full API kit and started testing the water. Did tests on 4-2-12 and all the tests came out perfect. No nitrite no amonia and 40 ppm nitrate. PH was at 7.5. on 4-8-12 i found one of the mollies the one i thought was a bit weird at first kind of mangled and stuck in the filter tube. Thought maybe the pictus cat messed with him. Than this morning my pictus cat is basically dead. A tiny bit of white flim seems to be hanging from him in certain spots and he's barely moving. I left him this morning but im fully expecting him tobe totally gone when i get home from work. My thought now is wanting to prevent a disease from spreading in the tank. Any precautions or advice on what i should do from here to save the other fish and keep tank safe for my new fish i want to buy soon. I actually have a couple kinfe on order i was supposed to pick up later this week.