Madagascar Rainbow

Most Madagascan rainbows in shops have been carrying the wrong label for decades. Seriously Fish notes that the species is still traded as Bedotia geayi, a real but different fish from the Mananjary system further south, and FishBase files the same animal under the spelling madagascariensis. The fish comes from short coastal streams and lower river reaches in the Atsinanana region of eastern Madagascar, many of them linked by the Canal des Pangalanes.

It reaches 10 cm standard length, and the tank recommendation follows from that: a base of 120 by 30 centimetres is treated as mandatory, which works out at 108 litres. Water in its home streams was logged across 23-32 °C within a single month, at pH 4.5-7.5, so this is a fish with a wide tolerance rather than a narrow target. FishBase's own maximum is smaller at 8.6 centimetres; this page keeps the Seriously Fish figure because the size column is defined as its standard length.

Keep eight or more. It is a schooling species, and males show their best fins and colour while competing for females, which a pair in a small tank will never do. It is also intolerant of accumulated waste, so weekly changes of a third to a half of the volume are part of the deal. Feed small live and frozen foods alongside dry, and avoid housing it with other Bedotia species, which it will hybridise with.