like Db junkie is saying everyones experience are different...my armatus doing great with bass, pikes ,bichir, st dat, cichlids, eel, nile perch all big size etc...except african tigerfish and it's own kind...in the 500gl...my armatus..i got him when he was 12" and I started to mixed him with different fish...now he is about 22inches as long the tankmates are bigger than the armatus....fish also have different personality..."RAIDER" is pretty calm conpare to the other armatus...just my opinion

dont get me wrong in the past he killed some of his tankmates or ate them......because they are smaller or other payara..like redtail payara.

I had mixed with aro with no problem..I feed him nothing bit feeders from 12inches to 22inches..last 2 weeks ago I decided to not feed him ..for about 3 days...raise my temp to 85 and did a 80 or 100 gallon water change also raise my ph from 6.5 to 7.0...and I started with tilapia fillet ...no luck..so I tried chicken hearts...he grab on it and then I also got me shrimp and ate that too...NO more feeders...but he likes the hearts more than the shrimps..... gl bro