If I had to pick only one species, it'd probably be pseudotropheus demasoni, they're among the most prolific mbuna I have (but probably because I have more of them than anything else).
These days I'm currently breeding demasoni & metriaclima sp. zebra 'chilumba'
Recent consolidation of demasoni fry from two mothers spat a day apart (1-2 days old in this pic):
Some larger zebra chilumba's (sired by the fish in my avatar):
I've got a female metriaclima sp. msobo due to release fry within the next few days, they're rare in my area but not sure if I want to retain her fry or not, due to space requirements and the aggressiveness of the species: