Q. Is a 10-gallon aquarium with a divider large enough to breed a pair of Melanochromis auratus?
A. Melanochromis auratus are not large, so your 10- gallon aquarium can work. They are aggressive, though, and a small aquarium leaves little room for the female to escape the male's attention. The divider may prove essential to the female's safety.
Dividers have proven to be particularly useful for large, boisterous substrate spawners because they protect a female from an overly attentive male. Such dividers are often made of plastic "egg crate" (the material is used as a diffuser for fluorescent lighting and is available in the lighting section of hardware stores), which has holes that will facilitate spawning. The female can lay eggs on one side of the divider and the male is able to deliver his milt from the other side, fertilizing the eggs. Both parents are able to see each other, the pair bond is maintained, and when the fry hatch and become free-swimming, they can swim through the divider to either side of the aquarium and enjoy the protection of both parents.
Like many African cichlids, Melanochromis auratus are mouth-brooders, and they provide more of a challenge when attempting to breed them using a divider. For one thing, mouthbrooders interact more than substrate spawners. As the female deposits the eggs, the male swims alongside or behind and fertilizes them. The female then spins around, picks up the fertilized eggs and holds them in her mouth. This process is repeated many times.
If a suitable spawning site, such as a flat rock or slate, is placed so that it protrudes on both sides of the divider, mouthbrooding cichlids may be able to spawn while separated. If this isn't possible, there are other options.
If the female is smaller than the male a "partial divider" can be used. Cut holes into the divider that are large enough to allow the smaller female to pass through, but small enough to block the larger male. The female will have access to both sides of the aquarium, and the male will be confined to one side. If he becomes overly aggressive, the female can escape to her own side of the aquarium. When the pair is ready to spawn, the female can enter the male's side. After the spawning she can retreat back to her own side with a mouthful of eggs, to incubate them while free from harassment.
A different version of this method is to use an upturned flowerpot with a hole cut in the side instead of a divider. The hole should be small enough to allow only the female inside the pot.
If both adults are the same size, keep the divider in place while you condition the pair for spawning. After a few weeks of conditioning, select a day when you are able to keep an eye on the fish, and remove the divider in the morning to allow the fish to interact. There will likely be some aggression between the two initially, so be sure it doesn't get out of hand.
If the female begins to take a beating, replace the divider and condition the pair for a longer period. On the other hand, you may observe them as they spawn. If spawning occurs, be ready to replace the divider and isolate the female once she begins resisting the male's advances. She will then need time to incubate and raise her babies, and to eat and condition herself before further interaction with the male.