Are you thinking of keeping what you have in there? If so, a full mbuna tank isn't realy an option. Requirements as far as food, pH, territoriality etc are concerned clash. If you stick to the more peaceful mbuna you may be able to manage it. You probably already know that the labs would work and the tinfoils should also be ok due to their size and speed (though, realy, they should be in a school in a bigger tank). If the plec is a common it'll eventualy need a larger tank but is otherwise compatible. The kribs mean you need to stick with the more peaceful species. Most mbuna are very aggressive fish and will not make life easy for the generaly smaller and less aggressive kribs (which are not even a rift lake species). TBH, if you want an mbuna tank you should get rid of everything you have now - except the labs (and possibly the plec though, like I said, that'll out-grow the tank anyway) - then I'd suggest iodotropheus sprengerae and pseudotropheus acei as good choices for tankmates. P. acei would also work if you did not remove those extra fish - it's one of the more peaceful mbuna. Besides these two species, I also reccomend p. saulosi and p. socolofi but these are a little more aggressive.
