Other mbuna african cichlids, a pleco, and some sort of synodontis type catfish are all I would recommend keeping with african mbuna cichlids.
I read that you haven't looked up the fish so let me give you a quick overview of them. Their behavior is unlike any other freshwater species. They are always moving and always after each other and are quicker and more aggressive than any other fw species which is why no other type of fish can be kept with them (barbs, gouramis, sharks, etc.). They are absolutely fascinating to watch though and love their owners. I have 8 adult mbuna's in a 55 and it's amazing the things they will do. They'll chase each other all day and then when I come over all of them will crowd into about a 10 gallon space right in front of me and basically interact with me. They transplant rocks like crazy as adults. It's just constant activity in that tank. They have a pecking order amongst themselves which is very evident as adults. This is the main reason non mbuna cichlids cannot be kept with them. They have a different pecking order and it nearly never works.
Bottom feeders also have a tough time with these fish and plecos and synodontis catfish are the only type of bottom feeders that can handle it. As an example of how aggressive they can be, when they were juveniles(about 2.5 inches) I tried to incroduce a pleco to the tank unsuccessfully 4 times before it worked. The plecos were always the larger fish but these guys can be voracious.
I would say about 4-5 more mbuna cichlids, 1 pleco, and maybe a catfish would be the max I would recommend. Anything over that would likely cause problems.
There are a alot of different types of mbuna cihlids to choose from so although this doesn't seem like alot of choice, it still a huge variety of colors and fish to choose from.
Also, how large are these fish now?
HTH
