Betta mahachaiensis

A member of the Betta splendens complex, close relatives of the familiar Siamese Fighting Fish.

Wild bettas are hard to identify, and fish in the trade are often mislabelled. Ask for the collecting locality, and keep populations separate to avoid crossing them.

Males are usually more colourful and develop longer fins than females as they mature.

Use tall stems or floating plants for shade, driftwood and small caves, with an air-powered sponge filter. Add small caves such as clay pots or lengths of pipe, and use a tight lid, because the warm, humid air above the water protects the labyrinth organ. There is no need to use peat, which is unsustainable. Leaf litter does the same job.

Shy and slow-moving compared with domestic bettas, spending much of its time in shade. It becomes bolder in a dim, well-planted tank.

A pair is the usual choice. Reports vary on keeping groups, and dominant fish may bully others.

Males can be territorial, but physical damage is usually limited when there is enough cover.

Not for a standard community tank. Keep it alone or with very peaceful fish that like the same water, such as some small rasboras and loaches, because bigger or more vigorous fish will intimidate and outcompete it. Do not mix it with long-finned fish, or with fin nippers. Small shrimp may be eaten.

Occurs only in brackish, tidal coastal swamps, at about 1 to 10 parts per thousand of salt in the wild. It can be kept in medium-hard to hard fresh or slightly brackish water.

A small predator of insects and other invertebrates. Offer plenty of small live or frozen foods for colour and condition.

Bettas seem especially prone to obesity, so feed small portions. Mouthbrooding males do not eat while holding eggs.

A bubble nester. The male builds a nest in a tube, a small cave, under a broad leaf or among floating plants, and he won’t usually tolerate the female nearby until it is finished. The pair spawn in an embrace, and he places the eggs in the nest. Eggs hatch in 24 to 48 hours, and the fry stay in the nest for 3 to 4 days. Give the female plenty of cover, and fit the tightest lid you can, because the fry need warm, humid air to develop their labyrinth organ.