i think if you started them in the tank as juveniles, they'd be ok for a little while. they max out at around 3.5 inches from what ive read, so you might need to bump up the tank size a bit at some point. but for the most part i think you'd be ok. 6 might be just a tad bit heavy though. maybe try 4?
Finally reached 6 tanks... oh god, this addiction is getting serious. 75g mbuna tank, 65g gold severum, 55g OB peacock breeding colony, 30g(36x18) growout, 20 long Dwarf Alto's, 10g fry tank.
If I die young bury me in... An 8x2x2 with versa tops and a large sump for adequate filtration;)