Why one of my discus doesn't want to eat since i bought him and the color is black. What is the problem? Thank you

Tell us more like ph.ammonia,nitrite,nitrate temperture,what you are trying to feed that will help us help you.

heat does do the trick and they enjoy temps of 85 normally anyway (which is pretty hot compared to other fish). If you just got him its probably being shy, otherwise there might be some bacterial infestation or some sort of hexamita. There are medications for that, but like bilbo said, heat could probably do you good before any treatment. I would observer the discus for severla days, and make sure to keep that wter crystal clear. Clean water can hlpa fish survive any infection much better then unclean water.

Maybe :Maybe he stress..Just wait for a few day and maybe he will eat.(he will be hungry)How long he does not eat?Good Luck. :)Let it get use to his new enviroment.

Welcome back k1drock hope you get into fh again!!