Giant kuhli loach

The giant kuhli loach is the largest of the eel-shaped Pangio loaches in common trade, reaching about 10 cm and carrying 8 to 11 broad, squared-off dark bars over an orange body. The tail is what separates it from its relatives: either entirely black, or marked with a large blotch at the base plus a second bar or row of spots further out, where the more familiar P. kuhlii and P. semicincta show only the basal blotch. It comes from the lower Mekong in Laos, Cambodia and Vietnam, and from streams in southeastern Thailand, living in shallow, slow water among leaf litter. Many of those forest swamps and backwaters sit on old peat, so the water runs brown, holds almost no dissolved minerals and can drop to pH 3 or 4. Like the rest of the genus it can gulp air at the surface when oxygen runs short.

In a tank it spends much of the day buried and comes out to work the substrate, taking mouthfuls of sand and sieving insect larvae and small crustaceans out through its gills. Wild gut contents also turn up detritus and plant material. Sinking dried food is accepted, though the fish does better for regular live or frozen daphnia, artemia and bloodworm. It is peaceful with anything it cannot swallow and there are no reports of it harming tankmates, but eggs and fry are fair game. Buy at least five or six of them. They gather in large aggregations in the wild and will happily cram into one cave together in captivity. Small soft-water species make the best neighbours, among them Boraras, Sundadanio, the smaller Rasbora and croaking gouramis.

A base of 60 by 30 cm, roughly 54 litres, holds a group. Soft sand matters more than the volume does, because coarse gravel stresses a fish that digs, can injure it, and blunts the sifting that makes the species worth watching in the first place. Hold the water at 21 to 26 °C, pH 3.5 to 7.0 and 0 to 8 dGH, filter it gently, and give it driftwood, dried leaves and dim light overhead. Two things catch people out: these loaches jump, so the lid has to close properly, and a juvenile is thin enough to swim straight into an uncovered filter intake. Do not expect fry. Spawning in this species has never been recorded, so every one you see for sale was collected or farmed rather than bred at home. The IUCN lists it as Least Concern.