Never had them breed in anything smaller than a 30 gallon, Never tried anything smaller though. I have better luck with mbuna if I keep a display tank with healthy active males of differrant species (avoid conspecific colour patterns). Lots of rocks and caves with good entrance and egress.
I keep my hens in another tank and feed them a rich diet of good veggies, brine shrimp, and trout pellets as a staple. Once I feel they're properly conditioned I introduce them to the display tank. Your display tank needs to be rocked well enough that each male has a well established and respected territory. You will likely see the female holding within a week or two.
I have a 60 gallon tall that I use for Metriaclima, Labidachromis, Haplochromis and Pseudotropheus all at the same time using this aproach.
I used to strip fry but have found that with experienced females, I get a lot more fry if I give her a quiet 20 gallon with lots of smaller rock work and let her spit.
Good luck champ, spawning is the most rewarding part of the hobby IMO.