Africans need to be in groups to spread aggression. You also need to have the right male to female ratio or the males will fight with each other or stress the females out enough to kill them (I've had it happen). I suppose it's possible to have a breeding colony of labs in a 29 but again, you would need the right ratio of genders. It's better to completely upgrade your tank to a 55 and add a dozen or so mbunas. You should really start doing more research on the fish you wish to keep. I did an insane amount of reading up before I got my Africans and it helped out a lot.