This article has been adapted from my longer article: Feeding African Cichlids. Much of the content is the same, but what you'll find here is condensed and specifically directed toward the feeding of Mbuna. The following suggestions are what I have found to work best for me after keeping Mbuna for several years — and believe me, I have tried all kinds of feeding regimen.
Foremost, Mbuna are algae-grazing cichlids. In the wild, they spend the hours of the day scraping algae found covering the rocky substrate. Mbuna have long intestines (4x their body length) designed to extract the proteins and carbohydrates from the hard-to-digest algae. Cows and other ungulates use several stomachs to digest grass. Mbuna, on the other hand, do it with only one stomach and a very long intestine. For this reason, it is a good idea to occassionally fast your fish — give them a day off — as this allows them to purge their intestines on a regular basis. Use caution when doing this because hungry Cichlids are aggressive cichlids.
Mbuna should always appear HUNGRY. If permitted, they would gorge themselves in captivity. Realize that in the wild, most cichlids (including Mbuna) rely heavily on foods with lots of fiber, such as blue-green algae and organic detritus. While these foods constitute the majority of their diet, they supply very little food value per gram. Consequently, these cichlids must eat continuously in order to meet their metabolic needs. With nature having established this feeding pattern, Mbuna will attempt to do the same in your aquarium, notwithstanding the superior nutritional value of the foods you provide them and the higher protein content as well. Consequently, nature has not placed a limit on their feeding behavior and so these fish know little satiety; they will overeat if allowed.
Feeding should be limited to 30 seconds, 2-4 times a day. In other words, their total feeding time should be limited to no more than 2 minutes per day. Mbuna are avaricious eaters and can consume a lot of food in less than 30 seconds. Remember, nature has conditioned these fish to eat small morsels of food throughout the day. Furthermore, smaller and more frequent feedings will reduce aggression among your fishes.
Feeding Mbuna the proper foods is critical to their health. The decomposition of improperly digested, or improperly excreted foods can irritate the intestinal wall, and stress the fish, giving an invasive parasite a foothold. This can often come about when a primarily herbivorous, algae-scraping cichlid (like Mbuna) is fed foods high in animal protein. Some aquarists prefer to feed their mbuna an "ocassional treat" of brine shrimp or krill. In my experience, this is not only unnecessary for growing up beautiful and healthy fish, but more trouble than it's worth. Furthermore, brine shrimp are soft and slimy, which can irritate the bowel (as described above). If you insist on feeding live foods, select a food with a hard exoskeleton such as mysis.
So then, what foods are best? A quality vegetable flake food (like those containing Spirulina) by itself is all that's needed. Note, Spirulina is rich in protein and should not be fed alone. If you use a pure Spirulina flake, mix it with another type of flake. By mixing the Spirulina with other ingredients, like fish meal, you will achieve a more balanced and desirable diet. Spirulina is an excellent source of Phycocyanin, which is the blue pigment derived from blue-green algae, but for yellow or red fishes to show their best color, additional vitamin sources must be provided. Furthermore, fish fed too much Spirulina, may in fact develop dark, irregular spots or stains along their sides, called Spirulina spots.
What about pellet foods? There is an ever increasing variety of commercially prepared pellet foods. It used to be that there were just a couple of pellet sizes; however, in the past decade manufacturers have developed a wider variety of sizes (e.g., Baby, Mini, Medium, Large). I realize that I'm perhaps stating the obvious, but smaller granules should be given to smaller fishes while larger pellets should be reserved for fishes over 4-inches. Since most Mbuna do not exceed 4½ inches, I recommend feeding them smaller sized pellets. Pellets are particluarly advantageous over flake foods when it comes to feeding larger cichlids since they tend to be messy eaters. Flake foods in this setting tend to dirty the aquarium.
More manufacturers are now offering pellets that sink and others that float. This can be helpful since some fishes (e.g., peacocks, frontosa) prefer to scoop food off the bottom and do better with a sinking pellet while others prefer the floating pellets (e.g., Utaka, Mbuna, Protomelas spp.). I have successfully mixed cichlids of both groups by simultaneously feeding a sinking pellet with one that floats. Additionally, mixing pellet sizes can also keep fishes of different sizes happy. Some manufacturers have even developed pellet foods with a variety of sizes in one container.
Are there other foods I can feed? The safest and most nutritious foods for Mbuna are those which are predominantly vegetable-based, such as peas, zucchini, carrots, spinach, and romaine lettuce. These are needed to help them retain the full intensity of their coloration because of the beta-carotene, canthaxanthin, and other vitamins they contain. They also help to reduce the incidence of intestinal blockages because of their high fiber content. These should be "prepared" before feeding them. Freezing these vegetables and then thawing them will soften them up, allowing them to be consumed quite readily. I have also found that boiling them softens them and allows them to sink to the bottom of the tank, although this practice does cause the vegetables to lose some of their nutritional value.
Mbuna are herbivores. Treat them as such, providing them with frequent feedings of vegetable matter, and you'll see excellent results. Frozen, live, or pellet foods are not necessary to achieve good growth and color and in fact may cause more harm than good.