If your looking for another fish for your 55, Salvini, Sajica, HRP, Jewel Cichlid or even another male Con of a different color variant if you like cons. You'll have to look for males of all of the above suggestions because a Con will breed with all of them except maybe the Jewel IDK if it could breed with them since they are from Africa but more closely akid to new world cichlids.
Wow I see a lot of baaad advice in this thread.. seriously, a Managuense or a Buttikoferi? The op has a 55 gallon tank.
What can work is Salvini, Archocentrus Centrarchus (Flier cichlid), raindbow cichlid, and many others of the Archocentrus and Cryptoheros genus. A Firemouth can also work.
I've also been interested in the firemouths =/ the only thing that sucks is that the only decent fish shop near me won't give refunds no matter what - if you bring the fish back, they just take it and that's that. I think I'll try a firemouth in the future instead of a JD. Thanks again peeps!
Aw dang, but I also just read that they can cross breed, and I really wouldn't want to have to deal with that lol (dunno if I could sex a firemouth or not).
The strangest combo i have seen was a full grown convict male in with a 9 inch rhom and they had been together for 2 years in the same tank 55 gal in a guys fish house although i think this was a one off and would'nt recomend it.