There are so many different fish in the world, at least 30,000 species, with new species discovered all the time (several hundred a year!).
In the wild they range in size from the whale shark that can reach 12 metres (40 feet) to the dwarf goby that only grows to 1 centimetre (0.4 inches).
Many of the 100+ species we keep and breed are threatened with extinction in the wild through habitat destruction, pollution and over-fishing. For some species, like the cichlids from Lake Victoria and Lake Barombi Mbo in Africa and the live-bearing goodeids from Mexico, our breeding programmes may be their only chance of survival.