Lake Malawi (Lake Nyasa) is found in the southern section of the East African Rift Valley. The lake is 600km long and has a maximum width of 80km. Its maximum depth is 700m. With a surface area of nearly 31000km squared, this is a very large body of water indeed. In fact, Lake Malawi is the third largest lake in Africa. Lake Victoria and Lake Tanganyika are slightly larger. The lake was formed approximately 1-2 million years ago.
Three countries, Malawi, Mozambique and Tanzania, bound the lake. Despite the shared waterfront, the majority of the lake is bounded by Malawi, hence the name. In the other two countries, the Lake Nyasa ("great water") name still prevails.
The lake is a very unique body of water. It is not salty, yet has a general high pH (7.5-8.8), general hardness of 4-6 dGH and a carbonate hardness of 6-8 dKH. Therefore, this body of water has soft to moderate hardness but high pH values. The water temperature remains between 24-26 deg C (76-78 deg F) year round. The lake has few rivers draining the lake; therefore the majority of water loss is by evaporation, hence the high salt/mineral (other than NaCl) content.
The lake has in general seven different habitats present. Habitat #1, the gradually inclining sandy zone. This habitat occupies the largest amount of coastline space (70%) and is home to many cichlid species. In these zones, some plants can be found, yet no major plant habitat exists.
Habitat #2, the rocky coast. A prominent feature of the lakes coast are the long mountain ranges that frame the lake both on its north-west coast and on its north-east coast. The rocky coast only accounts for 5% of the potential area available for fish to settle yet houses the majority of cichlids found in the mbuna group. From steep underwater cliff sides to gentle sloping, rock piled banks; this habitat is void of plant life but full of animal life.
Habitat #3, the intermediate zone. This is the zone where the rocky regions and sandy regions run into each other. Many different cichlid species, both from the mbuna group and the non-mbuna group (haplochromis) occupy these zones. There may be some plant life in these zones but limited only to the shallows.
Habitat #4, open water close to shore. This is open water that is close to shore and not deep. Not many cichlids inhabit this zone for the simple fact that food can be found closer to the bottom of the lake.
Habitat #5, open water far away from shore. This is open water a long distance from shore and deep. No cichlid species inhabit this zone, yet fish from other families do visit it frequently.
Habitat #6, deep-water zone. This habitat is classified as below the depth of 30M down to 250M. Below 250M, the water is toxic, contaminated by poisonous hydrogen sulphide not allowing the survival of higher organisms such as fish. In the deep-water zone, many larger cichlid species thrive, mostly feeding off other smaller fish.
Habitat #7, the river mouths and reed covered shores. In this habitat, many non-cichlid family fish thrive (from the river) as well as non-mbuna cichlids. The majority of plant life can be found here.
Lake Malawi is truly magical. With it's huge size, unique water conditions, various habitats and over 600 species of cichlids endemic to this lake, it is easy to understand the fascination people have with keeping Lake Malawi cichlids in the home aquarium.
Spreinat, Andreas. (1997) AquaLex catalog - Cichlids from Lake Malawi: Germany: Dahne Verlag GmbH