Siamese Algae Eater (Crossocheilus siamensis) Breeding Guide

The true Siamese algae eater is not bred in home aquaria; trade fish are hormone-induced on farms or wild migratory spawners.

Overview

The Siamese algae eater belongs to the genus Crossocheilus, a group of slender cyprinids from mainland Southeast Asia. According to Wikipedia, the fish is found across the Chao Phraya and Mekong basins as well as the Malay Peninsula, inhabiting streams, rivers and flooded forests during the rainy season. Within the aquarium trade the common name covers several closely related species, and the taxonomy of the group remains unsettled.

Sexing

Reliable sexing is only possible in sexually mature adults. Seriously Fish notes that mature females are normally thicker-bodied than males, but it is impossible to accurately sex young fish by external appearance.

Spawning Behavior & Trigger

In nature these fish are seasonal, migratory spawners. Seriously Fish reports that they undertake reproductive migrations, moving upstream during the drier months and in the opposite direction when water levels rise. This dependence on large-scale seasonal hydrology has not been replicated in captivity, which is the principal reason home spawning does not occur.

Common Challenges

The combination of migratory spawning triggers and a lack of confirmed captive reports means hobbyists cannot expect to breed the species. Commercially, propagation relies on hormone injection on dedicated fish farms rather than natural pairing. Aquarists seeking these fish should obtain them from such trade sources rather than attempting home reproduction.