What about African Cichlids. Do they require hard alkaline and water.
In Africa there are cichlids that live in rivers that have soft acid water (Pelvicachromis and Nanochromis species), and there are fish that live in Rift Lakes that have hard alkaline water (mbuna, Pseudotropheus, etc).
Africa has 3 main Rift Lakes, Lake Victoria, Lake Malawi & Lake Tanganyika. Lake Tangayika has the hardest water (GH above 400ppm) and most alkaline pH (above 8.5). Lake Malawi has softer water but it is still hard and alkaline, and Lake Victoria has the softest water out of the 3 Rift lakes, but it is still hard and alkaline.
If the pH is above 7.0, it is alkaline.
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You can increase the general hardness and pH by adding Rift Lake water conditioners. These are designed to increase the GH of water so it closely matches the natural water in Africa's rift Lakes. Limestone, sandstone, coral and shells will all increase the pH and slightly raise the GH but they generally won't increase the GH enough for Rift Lake cichlids.
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Biology covers all living things on this planet but doesn't dedicate itself to aquatic life. Whereas marine biology covers everything aquatic, fresh, brackish and saltwater.
Biologists and marine biologists have a good knowledge of water chemistry and animal physiology and behaviour. Some marine biologists specialise in freshwater fishes, some specialise in marine organisms (corals, starfish, seahorses) and some specialise in marine mammals.