Well wont be long before you need to move them. Maybe when they hit 5-6". The Asian Red tail Catfish would wipe out most fish anyway, so I wouldnt advise putting anything in there for the time being. Convicts may hold thier own. But they arent a show stunner.
They get even BIGGER and IMO the most aggressive of catfish. They are real terrors when they want to be. Not like the puppy RTC's who you can give them belly rubs and all that lovey dovey stuff. Makes me want an RTC Sooo Bad! We had one for a while in a 240, but it wasn't ours we were holding it for 4 months while the owner was on a buissness trip. One of the best fish I have ever set eyes on. It used to be sooo social too. For that 29 i say a Blue Acara. Another option would be some small Mbuna.