More like 50 gallon minimum, the only cichlids I would put in a 30 are the shellies, Mbuna need 50 at least.
With Mbuna I would only suggest other Mbuna, I have a pleco and a CAE with mine, luckily so far they have stood their ground.
Filter wise I suggest having 10x the gallons. Like in a 50 gallon you would want a filter that does 500gph (gallons per hour). In my 75g I have two filters one that does 350gph and the other does 400gph so in total 750gph (75 x 10).
If you want breeding stick with two species (depends on the size of the tank) having a ratio of 3-4 females to 1 male. Or like in my tank I have an all male tank, I feel as though it keeps aggression down because they aren't fighting over the females to mate.
Hope that helps some!