catfish are fine with discus. you may get a rouge one now and again that likes to latch on to the discus, but generally they are great. i have whiptails, bristlenose, banjos, corys, iquito tiger plecs, and hoplos in with my discus and theyre all good. used to have a royal whiptail that liked the taste of discus, but i think they got their own back as he mysteriously died one night...