Siamese Algae-eater Crossocheilus oblongus/siamensis and Crossocheilus langei

The Siamese Algae-eater is native to rivers, streams, and flooded forests of mainland Southeast Asia, including the Malay Peninsula, Thailand and Vietnam. It can grow to 16cm long but is usually much less. It is yellowy fawn coloured with a black stripe from snout to the end of its tail, although the stripe can be made less prominent when it is hiding. It is related to the carp family but doesn't have mouth barbels but has a V-shaped upper lip with a small fringe.

There are several similar fish with which it can be confused. The Red Algae-eater, C. langei, native to Malaysia and Sumatra, has a normal mouth shape with small mouth barbels and is often called the Siamese Algae-eater, particularly in the aquarium trade (both eat red algae). C. atrilimes is also similar. The Cambodian Logsucker, also called the False Siamese Algae-eater, Garra cambodgiensis, has a darker back and the Flying Fox Shark, Epalzeorhynchos kalopterus, also from Southeast Asian rivers and another carp relative that eats algae, is browner with much sharper defined black and brown lines. (Well out of its range, the Darter Characin, Apareiodon affinis, of South America also looks similar, but has the small extra "adipose" fin of the characin/tetra family.)