EntoStentor
Yup. I've (successfully) kept discus. Different schools of thought, a lot of strong opinions, and a few fanatics in the discus world. Some have misconceptions and insist on notions that don't match the science-- like extrapolating native water conditions for green and heckle species to brown/blue discus--
https://www.practicalfishkeeping.co.uk/features/articles/definitive-guide-to-discus-part-one?rq=discus guide part one
(also, some discus keepers are in a panic to grow them as fast and big as possible, as though it's vital to their health or survival, but note their wild sizes)
Imo re: original question:
Black Ghost Knife-- in a large tank, probably
Congo Tetras-- temperament okay, aggressive eaters but surface and mid water feeders, a bit on the active side for discus, but probably okay, can depend on your particular group of discus-- ime discus vary in temperament, I've had shy discus and boss discus
Roseline Sharks-- not always as peaceful as their reputation, case by case situation
Filament Barbs-- water's an issue, they're essentially a cool water fish, their upper limit barely reaches discus low limit; in general I wouldn't keep barbs with discus, anyway
Striped and Spotted Raphael catfish-- I kept them together, no problems
Clown Loaches-- I tried them with discus once upon a time in my early days, too pushy and active for discus,
Blue Botia Loaches-- similar to clown loaches
Regarding the guy keeping them in 74 degrees, that's the seasonal low limit for
some discus in
some locations, not a good idea long term. However, discus temperatures in the wild are not always as high as some think:
https://www.practicalfishkeeping.co...at-temperature-is-the-water-where-discus-live
