Q. I hope you can provide me with some basic information. First of all, I have a 48- by 31-inch, 90-gallon aquarium aquascaped with lots of rockwork. What are comfortable stocking limits for such a tank and what species could I mix successfully in it? Secondly, what do you think of Congo tetras as dither fish for a tank of Pseudotropheus zebra? Finally, are there any scavengers native to Lake Malawi and are they commercially available?
A. The choice of filtration system, as much as tank size, determines the safe stocking limits for a tank. So do the frequency and scale of the water changes you are willing to make. If you are using a high-capacity outside power filter (hang on the back of the tank design) in conjunction with either a canister filter or a large sponge filter, and if you are willing to change from one-half to three-quarters of the tank’s water every 10 to 14 days, a stocking rate of 10 to 15 small- to medium-size mbuna or eight to 10 somewhat larger haplochromines (Aulonacara, Protomelas, Placidochromis, Cyrtocara, Copadichromis) would not be unrealistic. Alternatively, you could house three or four of the larger haplochromines (Nimbochromis, Tyrannochromis, Dimidiochromis, Fossorochromis) safely in such a setup.
There are so many Malawian haplochromines that the number of possible combinations of compatible species is almost infinite. It thus makes more sense to offer you some general guidelines that you can apply to the selection of species available to you.
First of all, I do not recommend mixing mbuna with other haplochromines. Smaller non-mbuna, such as Malawi peacocks (Aulonacara species), utaka (Copadichromis species), and numerous species formerly referred to in the genus Haplochromis, but now placed in other genera (Protomelas, Placidochromis, Cyrtocara, Maravichromis), do not find their hyperactive rock-dwelling relatives comfortable tankmates. If you insist on mixing members of these two quite different species assemblages, you should restrict your selection of mbuna to the smallest and least aggressive representatives of the group available, such as Cynotilapia afra or the several Labidochromis species.
Secondly, do not mix species with similar male coloration. This is an invitation to serious interspecies aggression — the various males will treat each other as potential rivals for access to territories and to females. For their part, females are more likely to succumb to the overtures of an alien male if his courting appearance closely resembles that of a male of her own species.
Third, do not mix species with similar female color patterns. Females and juveniles share the same pattern of black markings. Because the quickest way to recognize hybrid fry is to compare their color pattern with that of their mother, the more different the female color patterns of fish sharing an aquarium, the easier it is to spot hybrids when they occur. This is not a trivial consideration given the tendency of Malawi cichlids to hybridize in the relatively cramped quarters of a home aquarium. For further advice on this subject, I refer you to my book, A Fishkeeper’s Guide to African Cichlids, distributed by Tetra Press.
As far as suitable catfish to help locate and consume excess food in the tank is concerned, you might consider the Malawian upside down catfish, Synodontis njassae, which has been exported to this country and is periodically available through commercial channels. Any of the riverine species exported from Zaire or Nigeria will do well in a Malawi cichlid community, and most are more attractively marked than S. njassae, which is basically an olive-brown fish marked with darker brown spots. The Lake Tanganyika Synodontis species also do well in a Malawi community tank.
I would be reluctant to keep Congo tetras with carnivorous mbuna, such as the larger Melanochromis species or Pseudotropheus crabro. Predominantly herbivorous species, such as P. zebra, tend to ignore fast-moving, midwater-dwelling tankmates if well fed. Thus, they would not pose much of a threat to Congo tetras. However, Congo tetras really prefer softer, less alkaline water than that required by Lake Malawi cichlids. You would be better off using large Australasian rainbowfishes, such as Glossolepis incissus (the red New Guinea rainbowfish), as dither in a Lake Malawi community. They are just as colorful and active as the Congo tetras, but will find the hard, alkaline water of a Malawi community much more to their liking.