Some of these fish are, ummm... how would you say... fertile. See the picture of the yellows on the left with black fins. Lil' Dudette is, well, quite active. She pops babies out on a regular basis, as long as I keep her happy with the water quality, tank mates, etc.
These fish are mouth breeders. Lil Dudette drops her eggs in the sand. Then Daddy (often Shaq - the purple fish on the right) comes along and fertilizes them. Dudette picks them up in her mouth and carries them until they hatch. She refrains from eating for 21-28 days while holding her eggs. Eventually you can see little eyes when she opens her mouth. And a few days later her offspring swim right out of her mouth into the open water.
Twice, I have noticed her carrying (picture a chipmunk with full cheeks) and pulled her from the tank during the holding period to protect the babes from evil tank mates. I've seen up to 8 babies come out of that little mouth. Mom returns to the tank and the babies are plunged into the "baby tank". I have been raising 8 of these babies for the past 6 or so months and I believe it is time. So last night, I netted the babes one by one and released them in the big boy tank. I created tiny hiding places so that the smart ones would survive the wrath of the others.
Farewell my babies. Hide wisely.