6 foot long tank is small for a full grown jardini. i would stick with cichlids if it was me. Try some vieja like argentea perhaps, should be sturdy enough to stand up to the RD.
I wouldn't try anything until you know how temperamental he is going to be. Mine is extremely aggressive and won't even let a Pleco in his tank. I've seen a lot of other owners on here say theirs aren't as aggressive so you might luck out and get one you can have tank mates with