Commentaires: The water in Lake Malawi is very clear most of the time and it contains very little nutrients. Most of our cichlids come from areas with rocks and even when they live most of the time over sandy substrates they often migrate close to rocky reefs or islands to breed. The rocks of the lake have a very rough surface and are derived from volcanic activity. In the upper 10-20 meters all rocks are covered with a combination of an algal matrix and sandy sediment. Depending on water currents (and wind in the upper layers) some rocky coasts have very little sediment in the shallow water while those of deeper regions usually have more. The water of the lake has a pH of about 8.3 and a conductivity of about 200-250 µS. The temperature of the surface water varies from 20°C in the windy season (June to September) to 30°C in the rainy season (December to April). At depths of about seven meters this fluctuation is less noticeable and varies between 22°C and 28°C.