I must be doing something wrong or he must be sick I dont know I bought a adult FLOWERHORN at my local fish only pet store a month ago they are much more knowledgeable than petco or any of those and put it in a 75G tank with a piranha which did not favorably for the red belly but he was very colorful and have been feeding him goldfish feeders and rosie feeders which he seems to nibble some in half and let the other half float around the tank till I get rid of it. When I first got him he was very colorful and it seems like in the last 2 weeks he's been losing color and I noticed a little bit of fin on his right side is missing today last week I went to menaces and got some river rocks for the bottom of the tank which made the water a little cloudy for a few hours and killed my new filters so not sure if that was smart I'm including some before and current pictures this is my first flower horn so I have no idea what kind he is if I should feed him someone else or what I should do different but please help if you can.

And currently 






And currently 






