The permanent stratification of Lake Malawi's water and the oxic-anoxic boundary are maintained by moderately small chemical and thermal gradients.

[11] The outflows from Lake Malawi into the Shire River are vital for the economy as the water resources support hydropower, irrigation and downstream biodiversity.

[11] The oxygen limit is at a depth of approximately 250 m (820 ft), effectively restricting fish and other aerobic organisms to the upper part.

[24] The Portuguese trader Candido José da Costa Cardoso was the first European to visit the lake in 1846.

[27] Later, after experiencing the unpredictable and extremely violent gales that sweep through the area, he also referred to it as the Lake of Storms.

Rhoades's crew found the Hermann von Wissmann in a bay near Sphinxhaven, in German East African territorial waters.

Gwendolen disabled the German boat with a single cannon shot from a range of about 1,800 metres (2,000 yd).

[30] On the other hand, Malawi claims the whole of the surface of this lake that is not in Mozambique, including the waters that are next to the shoreline of Tanzania.

The wrangle in this dispute occurred when the British colonial government, just after they had captured Tanganyika from Germany, placed all of the waters of the lake under a single jurisdiction, that of the territory of Nyasaland, without a separate administration for the Tanganyikan portion of the surface.

[43] Lake Malawi has for millennia provided a major food source to the residents of its shores since its waters are rich in fish.

[44] Other species that support important fisheries include the Lake Malawi sardine (Engraulicypris sardella) and the large kampango catfish (Bagrus meridionalis).

[50] The IUCN recognises 117 species of Malawi cichlids as threatened; some of these have tiny ranges and may be restricted to rocky coastlines only a few hundred metres long.

As typical of utaka, Copadichromis azureus has bright blue males (shown) and duller females that are silvery with dark spots.

Aulonocara stuartgranti is part of a group of relatively peaceful species popularly known as peacock cichlids.

Fossorochromis rostratus is an "aberrant" hap that often sifts mouthfuls of sand to extract small food organisms.

Like many mbuna, Pseudotropheus saulosi is a small cichlid where both male (blue and black) and female (yellow) are colorful.

[57] Lake Malawi is noted for being the site of evolutionary radiations among several groups of animals, most notably cichlid fish.

[10][44][60] The Malawi Oreochromis mainly feed on phytoplankton, reach lengths up to 26–42 cm (10–17 in) depending on the exact species, and are mostly black or silvery-gray with relatively indistinct dark bars.

[10][60][68] Male chambo have unique genital tassels when breeding, which aid in egg fertilisation in a manner comparable to the egg-spots on the anal fin of haplochromines.

Among the non-cichlid native fish are several species of cyprinids (in genera Barbus, Labeo and Opsaridium, and the Lake Malawi sardine Engraulicypris sardella), airbreathing catfish (Bathyclarias and Clarias, and the kampango Bagrus meridionalis), mochokid catfish (Chiloglanis and Malawi squeaker Synodontis njassae), Mastacembelus spiny eel, mormyrids (Marcusenius, Mormyrops and Petrocephalus), the African tetra Brycinus imberi, the poeciliid Aplocheilichthys johnstoni, the spotted killifish (Nothobranchius orthonotus), and the mottled eel (Anguilla nebulosa).

[71][72] The endemic freshwater snails are all members of the genera Bellamya, Bulinus, Gabbiella, Lanistes and Melanoides.

[73] Lake Malawi is home to a total of four snail species in the genus Bulinus, which is a known intermediate host of bilharzia.

This change, first noticed in the mid-1980s, is possibly related to a decline in snail-eating cichlids (for example, Trematocranus placodon) due to overfishing and/or a new strain of the bilharzia parasite.

[80] These swarms, typically appearing far out over water, can be mistaken for plumes of smoke and were also noticed by David Livingstone when he visited the lake.

[80][81][82] The aquatic larvae feed on zooplankton, spending the day at the bottom and the night in the upper water levels.

[82] The adults are very short-lived and the swarms, which can be several hundred metres tall and often have a spiraling shape, are part of their mating behaviour.

[81][82] In January 2015, a sediment control tank collapsed at the Paladin Energy-owned uranium mine in Northern Malawi after a high intensity rain storm hit the area.