Gastromyzon stellatus

Gastromyzon stellatus has the characteristic flattened body typical of the genus, adapted for life in strong currents. The base colour is dark brown, with numerous small yellow spots scattered across the body and head, which is reflected in the species name. Adults reach about 5 cm in length. Sexual dimorphism is weak: females usually appear more rounded, while breeding males may develop noticeable bumps on the head.

The species is endemic to Borneo, found in the Sarawak, Sadong and Lupar river basins. It inhabits shallow streams with fast-flowing, clear and oxygen-rich water. It prefers areas with rocky or pebbly substrate, where biofilm of algae and microorganisms develops on rocks and boulders.

This is a peaceful, daytime-active fish with a bottom-dwelling lifestyle. In nature, gastromyzons occur in small groups, so aquarium keeping should be in a group of at least 4 individuals to show natural behaviour. They are compatible with other small, peaceful fish preferring similar conditions, but may lose out in competition for food to faster-moving species due to their feeding habits.

Keeping requires an aquarium with powerful filtration and aeration providing strong flow and a high level of dissolved oxygen. Fine pebbles or sand work as substrate; smooth rocks and driftwood are essential for the fish to graze on. The tank should be mature, with an established ecosystem and natural algal coating on the décor. A tight-fitting lid is necessary, as these fish can move across glass above the water level.

In nature it feeds mainly on algal growth and microorganisms (biofilm). In the aquarium, the diet is supplemented with quality sinking tablets for catfish, specialized plant-based pellets, and small frozen foods. It is important to provide abundant algae on rocks, as constant scraping of food is central to their survival.

Breeding in the aquarium is extremely difficult and happens rarely. Spawning is pairwise; males prepare small depressions in the substrate under rocks where the female lays eggs. After fertilization, the male may cover the clutch with substrate. Fry appear after some time and begin feeding on microorganisms on surfaces. No specific conditions for stimulating reproduction in the home aquarium have been developed.

The species is sensitive to water quality, especially accumulation of nitrogenous compounds and low oxygen levels. Under poor conditions, fish quickly lose activity and are prone to bacterial infections. Prevention consists of maintaining cleanliness, stable water parameters and high aeration. Aggressive medication is not recommended unless absolutely necessary.

When buying, choose active fish that constantly move across surfaces or glass, scraping food. Avoid specimens showing signs of emaciation, damaged fins or lethargic behaviour. A healthy fish should have a robust body and clean surfaces with no white coating or sores. It is preferable to obtain specimens that have already adapted to aquarium conditions and accept the offered food.