Gastromyzon scitulus

Gastromyzon scitulus is a small fish, reaching 4–4.5 cm in length. Its body is strongly flattened dorsoventrally, which, combined with wide, horizontally positioned pectoral and pelvic fins, forms a powerful suction cup, allowing it to cling to rocks in strong currents. The body coloration is dark, with numerous light cream spots that also cover the fins. Sexual dimorphism is evident in females typically being larger and having a more rounded body shape, while mature males develop characteristic raised growths on the first rays of their pectoral fins.

The species is endemic to the island of Borneo, inhabiting tributaries of the Sadong River basin in Sarawak, Malaysia. In nature, it lives in shallow, fast-flowing mountain streams with clear, oxygen-rich water. It prefers areas with stony, gravelly, or rocky substrates covered with a biofilm of algae and microorganisms.

A peaceful but territorial fish. Intraspecific interactions often manifest as display behavior and competition for the best feeding spots, but serious injuries are rare. They are bottom-dwellers, moving across surfaces using their suction cup. It is recommended to keep them in a group of 4 or more individuals to observe their natural social behavior.

An aquarium with good aeration and strong current, mimicking a mountain stream, is required. It is essential to have a large number of smooth stones, boulders, and snags covered with algal growth. Lighting should be bright enough to stimulate algal growth. The substrate should be fine gravel or sand. A tightly fitting lid is necessary, as these fish can move across glass and may escape the aquarium. Stable water parameters are critically important, so stocking is only permissible in biologically mature aquariums.

The main diet in nature consists of algae and the microorganisms living within them. In the aquarium, fish accept high-quality dry foods in the form of tablets or wafers, as well as frozen foods such as bloodworms or brine shrimp. It is important to provide a varied diet and natural biofilm on rocks, as fish can suffer from a lack of plant matter in their diet.

Breeding in an aquarium is difficult. Spawning is stimulated by increasing water temperature and abundant feeding. Eggs are laid on hard surfaces, and incubation lasts about three days. Fry are photophobic and require very fine starter food, such as infusoria, due to their extremely small size at hatching.

There are no specific characteristic diseases, but the fish are extremely sensitive to low dissolved oxygen levels and organic water pollution. They often arrive for sale in an emaciated state, which requires special attention to their acclimatization and quarantine. Prevention involves maintaining water cleanliness and high levels of aeration.

When purchasing, choose active fish that are constantly moving across surfaces in search of food. Avoid individuals with signs of emaciation, sunken bellies, or skin lesions. It is recommended to inquire about the keeping conditions at the store and ensure quarantine before placing them in the main aquarium.