FishProfiles.com Message Forums

While trawling the web for something else, I alighted upon this nice little article (Adobe PDF document, 419KB in size):

Food Switching In Wild Mbuna

This has some interesting implications for Mbuna maintenance in the aquarium.

Among the observations made by the authors of the document are:

[1] Switching between different food sources is ounced in juvenile fishes - juvenile Mbuna in the wild will alternate between rock grazing of aufwuchs, feeding upon planktonic organisms in the water column, and even predation upon other fishes' eggs and fry;

[2] Mature males defending a breeding territory switch feeding modes much less frequently, and are more heavily dependent in the wild upon the algal mats growing upon the rocks forming their chosen territories;

[3] Adult females and subadult males exhibit a transitional behaviour between the above two extremes.

While it has been known that Mbuna in particular need vegetable matter in their diet, and foods containing exclusively high-protein animal matter lead to the infamous "Malawi Bloat" condition, this document confirms that the fishes are not exclusively herbivorous, something that quite a few aquarists have thought for some time. Indeed, the aufwuchs mats upon which the fishes graze contain their own endemic fauna, and individuals from this fauna almost certainly end up in the stomachs of wild Mbuna.

However, the foods selected by the Mbuna are energy rich, but not necessarily protein rich - at least not in terms of crude animal protein of the kind that finds its way into many manufactured aquarium foods. While the protein content of some food items (e.g., the eggs and fry of other, smaller fishes) may provide boosts in protein intake when opportunity arises, the food cycle of these fishes is, according to the authors characterised by two principal factors:

[1] Predictable food sources, namely the aufwuchs mats;

[2] Unpredictable food sources of wildly varying abundance, namely the planktonic organisms in the water column.

All of the fishes in a given region will turn to the aufwuchs mats in times of planktonic shortage, and those fishes equipped to graze most effectively upon these mats and gain sustenance upon them are the ones whose genes will predominate in future generations. However, while the dentition and oral cavity structures of these fishes initially led scientists to consider them as being (to use the jargon) trophic specialists, this specialisation is now regarded as facultative rather than obligate - the fishes can capitalise upon any handy food source and are only restricted to large scale aufwuchs feeding when plankton is in short supply.

So, the paper appears to suggest that aquarists should intersperse live foods with vegetable matter - something quite a few mbuna keepers here no doubt already do - but the intake of high protein flake should be watched closely to ensure that "Malawi Bloat" doesn't take a hold. Plus, flake and tablet foods for Mbuna should be selected that contain a considerable proportion of vegetable matter. Fortunately, some manufacturers are responding in kind, and specialist foods with significant plant content are appearing in the marketplace - Tetra has released two such foods, the TetraVeg flakes and TetraPor Vegetable crisps, and other manufacturers such as Aquarian and NutraFin boast similar additions to the range.

However, it's nice to know that someone took the trouble to go out and spend hours watching these fishes feeding in the wild, so that we now know what they really get up to outside of the aquarium.


Panda Catfish fan and keeper/breeder since Christmas 2002