A 29 is a bit tight for mbuna. They really need at least a 3' tank, a 4' is even better. A 55 gallon is a perfect mbuna tank. If you decided to set up a 55 for him you could get a lot more. I have well over 20 mbuna plus catfish in my 55 gallon. But most of them are babies still.
If you set up the 55 gallon pretty much he can only go with other mbuna and some species of syno catfish. These guys are very aggressive, but are also very colorful. There are tons of mbuna species out there to choose from. For a 55 gallon I would pick 3 species you really like and have 5 of each, with one male to four females.