I very often hear of cichlid keepers with mixed tanks. Some keep New World and Old World cichlids together. Some keep Tangs with Malawis and some even keep West Africans with East Africans. Does it really matter? Sure….sometimes. It depends on several factors.
What about keeping mbuna with Tanganyikan shell dwellers? “Blasphemous!” some might say. I would say, “Not so fast.” Different lake origins and water parameter requirements aside, it can be done. I know because I do it. But should you?
As for water parameters, I wouldn’t worry about that unless you are purchasing wild caught specimens. Most cichlids sold in the US are bred domestically in water that parametrically doesn’t identically match their endemic lake water. Nonetheless, you should still strive to keep either of these fish in hard, alkaline water.
“But wait, don’t mbuna require a more vegetable based diet?,” you ask? Yes, mbuna and most Tang shell dwellers subsist on different diets in the wild. However, there are some important points to remember. Mbuna are larger, have larger mouths, and eat more by body weight. Why does that matter? Because shell dwellers are so much smaller, have smaller mouths, and eat less, you can feed them very small flakes or pellets that mbuna will mostly ignore. Furthermore, because these two types of fish don’t occupy the same areas of their respective lakes, they will largely ignore each other if kept together in a tank. Also, remember that mbuna are not predators, so they pose no real threat to the shellies, even though the mbuna are much larger. In addition, the mouths of mbuna aren’t designed to eat other fish so even if the mbuna wanted to, they could not consume the shellies whole, like many predatory cichlids do.
I keep three adult male ‘Lamprologus’ caudopunctatus shell dwellers in a 75g with a couple of adult mbuna (a Labidochromis sp. ‘Red top Hongi’ and a Labidochromis caeruleus). As would be expected, the mbuna pay no attention to the caudos. Of course, these are no mated pairs in this tank and thus there is no spawning activity. Keeping any fish together when a pair spawns can be a dicey situation, regardless of genera.
I feed the caudos normal cichlid food and I feed the mbuna purely spirulina and/or algae-based foods. Do the mbuna sometimes eat the caudo food? Yes, but I feed both types at the same time in different areas of the tank. The pieces of caudo food are so small that the mbuna tend to ignore them most of the time. Do the caudos eat the mbuna food? Yes, sometimes, but when the mbuna approach their own food, the shellies disperse. Shell dwellers are typically more opportunistic feeders, so consuming algae or spirulina foods present no physiological problems for them.
I have kept these fish together for over a year and have had no problem. Some might suggest that I run the risk of Malawi bloat with the mbuna eating some of the shellie food. That has not been the case. In addition, neither types of fish pose a threat to the other. When the mbuna approach, the caudos will sometimes disappear into their respective shells. I think this is more of a predator reflex than anything. So, yes you can keep mbuna and shell dwellers together successfully under some circumstances. I am not suggesting that you do it, but under similar circumstances and conditions as mine, you can do it.