I have discus with other fish.... They seem to be fine. theyre in a 4ft by 2ft high tank.300litres. there are 9 discus(5 juvenile), 10 cardinal tetras, 8 blackwidow tetras, 5 mollies, 4 borneo suckers, 1 clown plecostomus 4 1\2 in, 1 ghost knife 9in, 1 pictus catfish 4in.... In my 2x2x2 200liter tank i had 2 juvenile discus, 1 10in ghosht knife, 3 blue rams, 2 gold rams, 10 black widows, 15 columbian tetras, 2in gold spotted pleco, 4 1\2in bristle nose. So yeah it can be done. I keep the tank at 29C. Both are reasonably planted with anubius and thin val. I have good fitration on both, and do PWC every 2-3 weeks.