Can be done. Most discus, whilst not growing long, grow high enough and somewhat thick enough such that the Knife and Aro can't consume them. Captive stunting really affects fish like Aros and CKs, but discus not as much.
Had it been Silver, it can work.
Though your RTG is tamed, just cannot trust upon these freaks. Though it cannot swallow discus fully, it possesses capability of constantly stressing them out. Stressed discus do not look good.
just depends on your fish. some will coexist with discus. others, not so much. just keep an eye on it when you introduce them. i know of many people who heep their aro(rtg, silver, jardini) with discus. it just depends on your fish's personality. goodluck =]
I have a 2 1/2" silver aro with two silver dollar sized discus and they get along well. I want to know the answer to the question too... I just purcashed a 120 tall and would like to put some young discus and aro's until they outgrow the tank in a year.
Can I keep them together?
Should I just buy separate tanks?
The mix of the two would be absolutely beautiful to watch...