Knight Goby

The knight goby is a stocky little goby of around 9 cm, pearl-grey washed with blue and scattered with black spots. Two dorsal fins crown it: the first, stiffly rayed, is raised like a fan by mature males. Females stay smaller, rounder in the body and often yellower in tone. It lives in the estuaries and tidal zones of South and Southeast Asia, from Pakistan and India to Indonesia by way of Sri Lanka, Thailand and Malaysia. Despite its brackish reputation it turns up more often in fresh water, over sandy beds cluttered with roots and stones. Allow 120 litres, fine sand and a wealth of caves: territorial towards its own kind, it needs as many retreats as there are fish. Hard alkaline water suits it, though it fares better with a little salt (1.005 sg). An omnivore, it also grazes algae. Skip dwarf or long-finned tankmates: anything that fits in its mouth is eaten. It spawns in caves, the male guarding up to a thousand eggs.