Hi everyone, i would greatly appreciate any advice you can give me. I have a 55 gal tank with five discus that i purchased about three months ago, I make sure to keep the water very clean and as suitable as i can for them so I do three 50% w/c a week straight from the tap and then I add aquarium salt and aquaplus to the water. My ph is a little high (7.6) but they seemed to adapted pretty well. I feed them frozen bloodworms and pellets and flakes. My Aquarium Techs are: ammonia levels are at 0 and my nitrate and nitrite levels are also good. My temp is 84-86 and the fish are about 3 in. I got them from a local breeder on long island. i have a fluval 305 which is awesome, with two slots of biomedia on the bottom, two slots of cotton or floss in the middle and two slots of the aquaclear sponge on top, and I clean out my filter every two weeks. I have a fluorescent aquarium light on top that i leave on for about 10 hrs a day, my tank has gravel on the bottom and has decor and many places for them to hide. For the most part they adapted and have been doing very well since I first purchased them, until recently (about two weeks ago), one of my fish has been in really bad shape. For some reason all of sudden, he stopped eating, swimming, or doing anything for that matter. He is very dark most of the time and he looks like he’s about to die. I cant put a finger on whats wrong b/c all the other fish seem to be striving. i am not sure if his poop is white, I am pretty sure it isn’t bc then I would’ve noticed it, he just appears to be really sick and I don’t know what to do. I am willing to buy a 10 gal and a heater etc.. so I can quarantine him, but I don’t know wha to put in the water or to feed him that is going to help. Any help would be greatly appreciated, thanks so much everyone.