Formosa Loach

Adults of this species reach a length of 9–10 cm. The fish's body is noticeably flattened, and its ventral and pectoral fins are very wide, resembling a fan. With their help, it clings tightly to the surface of large boulders. This anatomy, combined with a specialized mouth structure resembling a sucker, allows it to effectively withstand strong currents. The caudal and dorsal fins, in contrast, are small. The coloration is usually gray or brownish, complemented by a pattern of light spots.

The native habitat of this fish is the eastern part of Asia. It is endemic to Taiwan, an island located off the coast of China. The Formosa Loach inhabits numerous mountain streams and small rivers that flow down from the central mountain range. Typical biotopes are shallow, fast-flowing streams with many cascades and rapids. The bottom of such bodies of water is strewn with stones, boulders, and also snags that get stuck in various places. Aquatic plants are rarely found in the main channel; they are usually located along the banks. Streams and rivers exposed to sunlight promote the formation of a biofilm of algae and microorganisms on the stones, which is the primary food source for these fish.

This fish has a peaceful and calm disposition, coexisting well with its own kind and with other species capable of adapting to conditions of strong currents. Among such tank mates, some large danios, Akysis catfishes, Gastromyzon, and other loaches can be distinguished. It should be noted, however, that the latter are not always friendly.

For a small group of these fish, an aquarium should have a volume of at least 100 liters. A key aspect of caring for the Formosa Loach is providing high-quality water with abundant oxygen content, as well as creating a powerful internal current. These conditions can be achieved by installing a high-performance internal filter or a combination of several filters, which, in addition to purification, will serve as a source of intense water movement, mimicking a mountain stream. It is recommended that the water volume be renewed 10–15 times per hour; for a 100-liter aquarium, this means a filter capacity of 1000 liters/hour. An important factor in maintaining water quality is regular aquarium maintenance, which includes weekly partial water changes and timely removal of organic waste (food remnants, excrement). The aquarium decor should use elements that replicate the natural biotope: stones, boulders, and snags. Natural snags under bright lighting will create a basis for algal growth, providing an additional food source. Live plants are usually not used, but some species that can attach to wood (e.g., Anubias, Bucephalandra, certain types of mosses and ferns) can be utilized.

The natural diet of these fish primarily consists of algae, with small invertebrates playing a secondary role. In the aquarium, nutrition should also be based on plant components. Live or frozen foods such as bloodworms, Artemia, and Daphnia can be a good supplement, but protein products should be offered in limited quantities. Some manufacturers offer special gel-like (paste-like) foods in tubes. These foods can be an optimal choice, especially given the need for strong currents: in turbulent flows, any other granulated or flake foods will quickly disperse throughout the aquarium.

At the time of collecting information for this article, no reliable data on successful breeding of Formosa Loaches by hobbyists in home aquariums were found.

Health problems in these fish arise only in the presence of injuries or keeping in unsuitable conditions, which leads to a weakening of the immune system and the subsequent occurrence of various diseases. At the first signs of illness, it is necessary first to check the water parameters for exceeding permissible values or the presence of toxic substances (such as nitrites, nitrates, ammonia). If deviations are found, all indicators should be normalized, and then treatment should begin. More detailed information on symptoms and treatment methods is available in the "Diseases of Aquarium Fish" section.

When purchasing, it should be noted that this species is a rare guest in the aquarium trade and often enters sale as an accidental bycatch during the import of other loach species from Taiwan. Due to transportation peculiarities and high water quality requirements, individuals can be severely emaciated or weakened, so it is important to carefully assess their condition before acquisition.

• choose fish that are actively moving on surfaces or glass, rather than lying motionless on the substrate in an apathetic state;
• avoid specimens with sunken bellies, signs of fin damage, or an unnatural film on the body;
• ensure that the aquarium with the fish maintains a strong current and high aeration, as the absence of these conditions in the store quickly leads to a deterioration in the health of the individuals.