Gastromyzon cornusaccus

Gastromyzon cornusaccus is a small fish, reaching about 5 cm in length. Its body is highly flattened, which, combined with modified pectoral and pelvic fins, forms a powerful suction disc, allowing it to cling to rocks in strong water currents. Adult specimens have a uniform body coloration, while juveniles exhibit a characteristic pattern of cream stripes and spots. Sexual dimorphism is weakly expressed: females are usually larger and have a wider body, which is noticeable when viewed from above or below.

The species is endemic to the island of Borneo, inhabiting the Sungai Kinarom River in Sabah, Malaysia. Its natural habitat consists of shallow sections of mountain rivers with fast currents, clean, and oxygen-rich water. The fish dwell on rocky bottoms among boulders and pebbles covered with a biofilm of algae and microorganisms.

This is a peaceful but territorial species, leading a benthic lifestyle. The fish prefer to live in groups, so it is recommended to keep at least 4 individuals to observe their natural behavior. Within the group, demonstrative skirmishes for the best feeding spots are possible, which rarely result in injuries. They are compatible with small, peaceful inhabitants of rheophilic aquariums that can thrive in strong current conditions.

For keeping, an aquarium with powerful filtration is necessary to ensure a strong current and a high level of dissolved oxygen. It is important to use a mature aquarium with an abundance of smooth rocks and pebbles on which algae actively grow. A tightly fitting lid is essential, as the fish can move along the glass and may leave the aquarium. Water parameters: temperature 20–24 °C, pH 7–8, hardness 2–15 dGH.

In nature, they primarily feed on benthic algae and associated microorganisms. In the aquarium, they accept high-quality dry foods, frozen, and live foods such as bloodworms, but the main part of their diet should consist of plant-based components. To maintain their health, it is important to ensure a constant presence of aufwuchs on rocks or to use specialized vegetable foods.

Breeding in an aquarium is extremely difficult and practically unstudied. There are only isolated descriptions of spawning attempts, which required imitation of seasonal temperature changes and specific flow conditions. Eggs are laid on the substrate, and fry are extremely demanding regarding water quality and the availability of natural food.

Fish are sensitive to water quality and oxygen levels. Under poor keeping conditions, they are prone to bacterial skin infections and ectoparasite infestations. It is important to avoid overheating the water, as high temperatures reduce the content of dissolved oxygen, leading to a weakened immune system. Signs of ill health include refusal to eat, emaciation, and the appearance of whitish spots on the body.

When purchasing, choose active specimens that constantly move across surfaces and scrape for food. Avoid fish showing signs of emaciation, sunken bellies, or skin damage. Healthy individuals should appear plump and exhibit natural behavior, clinging to decorations or glass. It is recommended to ask the seller what the fish were fed in the store.