Trigonostigma espei
Varies with locality. It most commonly inhabits gently flowing sections of forest streams and tributaries where submerged aquatic plants grow thickly. The water is sometimes stained faintly brown/yellow due to the presence of tannins and other chemicals released by decomposing organic matter and the substrate scattered with fallen leaves, twigs and branches.
Such environments characteristically contain soft, weakly acidic to neutral water and are often dimly-lit due to dense marginal vegetation and the forest canopy above.
In Krabi province, southern Thailand it can be found living in a particular karstic (limestone) area with neutral to alkaline water (pH 7.0-7.4). The habitat consists of a series of deep limestone sinkholes forming pools at the surface, plus a small ditch which acts as an overflow from the pools.