Order Siluriformes
Family Loricariidae
Subfamily Hypoptopomatinae
Genus Otocinclus
Otocinclus inhabit slowly flowing rivers with cool, oxygen-rich water, as well as small lakes and ponds overgrown with aquatic vegetation in northern and central South America. One of the smallest representatives of the family. Length up to 4 cm. The genera Hisonotus and Parotocinclus have been separated from the genus Otocinclus. The most commercially available species are O. macrospilus, O. vittatus, and O. hoppei. During acclimatization, they must be fed with live food at first.
The difference between Otocinclus and Parotocinclus. It is quite easy to distinguish them, as the former has an adipose fin, while the latter does not.
All members of this genus have a streamlined, flattened body shape and a sucker-like mouth apparatus that allows the fish to hold on in a current while scraping off various algal growths and small living organisms; in fact, algae make up the bulk of their diet. Representatives of the genus lack both an adipose fin and a swim bladder. The body is covered with bony plates. The snout is pointed. One of their most important features is the pelvic fins, which they use to hold onto plants. Externally, an Otocinclus resembles a tiny dolphin. This is one of the fish species that can be recommended for keeping with shrimp or in nano-aquariums.
All representatives of this genus have a similar coloration — a typical dark grey to black lateral stripe. Depending on the species, it is wider or narrower, running the entire length or not, and may consist of fragments. There is always a large spot on the caudal peduncle, while its shape, size, and color vary. The back is always beige-black, dotted with small spots. The underside is always light, in most cases slightly translucent. Each species has a specific appearance that makes them really easy to tell apart. Females are larger and plumper than males. They live up to 5 years.
All fish species of this genus are schooling and keep to the bottom layer of water. These fish are quite sociable, so they should be kept in a school of 5 or more individuals. The aquarium must be well planted, with driftwood and shelters needed. These fish love having plenty of plants with large leaves and stones in the aquarium from which they can graze on algae. Due to the small size and peaceful nature of Otocinclus, tank mates must be chosen to be small and peaceful. Under no circumstances should they be kept with other sucker-mouth catfish, cichlids (even small and non-predatory ones), or other algae-eater species. Ideal neighbors for them are Corydoras and tetras.
It is very important that they are introduced into an already established and matured aquarium, as Otocinclus are quite sensitive to fluctuations in water parameters, as well as to the presence of ammonia and nitrite in the water. They prefer soft, slightly acidic water. They cannot tolerate very hard and alkaline water. Filtration should be strong, preferably through peat, and requires aeration and weekly water changes.
Main diet: algal growths and small aquatic organisms. These fish thoroughly clean aquarium glass, plants, and stones from algae; in fact, Otocinclus are specialists in diatom growths, and they will not allow brown film to develop on leaves and stones. These fish are true “cleaners,” so they are very well suited for a community aquarium. They cannot compete with other herbivorous fish. Part of the food should be given before turning off the lights. The catfish find food at night when the aquarium lights are off and their tank mates are resting.
The fish bring great benefits to the aquarium by cleaning it of algal overgrowths. They work practically around the clock searching for algae, yet they do not harm the plants growing in the aquarium. Otocinclus cope wonderfully with green, red, and diatom algae. For instance, major problems arise, especially for beginner aquarists when starting a new aquarium, when so-called diatom algae appear and cover the aquarium glass, plant leaves, stones, etc., in a continuous layer. A small group of Otocinclus will help quickly resolve this problem.
Driftwood is essential to provide ballast and cellulose, which are necessary for digestion. They can be fed with vegetable flake food. They readily eat vegetables (zucchini, eggplant, raw potato, blanched spinach or lettuce, cucumber, and bell pepper); at first, the catfish will ignore them, but once the vegetables become slightly saturated and softened, the fish will start feeding. Water temperature should not be below 20°C. They live 4-5 years. Hardness 2-15°, pH 5.0-7.5, temperature 20-26°C.
— Zebra oto — Otocinclus cocama [Reis, 2004]. (English — Zebra Oto). South America, Peru, Ucayali and Marañón rivers; found in large numbers, often among vegetation in the upper water column or near the surface of slow-flowing waters. 3-4 cm. The main color of the head and back is bluish-white or slightly yellowish-creamy, the top of the head and between the nostrils is black, and the lower part is pale yellowish. The sides of the snout and the postorbital region of the head are black, with a V-shaped white stripe on the tip of the snout.
The coloration of the back and sides is formed by four elongated black or dark grey saddle-like spots: one at the beginning of the dorsal fin, the second behind the dorsal fin, the third between the dorsal and caudal fins, and the fourth at the base of the caudal fin. There is a black spot on the caudal peduncle. The caudal fin has a W-shaped vertical stripe and a narrow band along the edge. The female is rounded and larger than the male (more visible from above).
The aquarium must be well planted, with driftwood and shelters needed. A sociable, peaceful fish that should be kept in a group of at least 4 individuals. They prefer mid-water levels. Due to the small size and peaceful nature of Otocinclus, tank mates must be chosen to be small and peaceful. Under no circumstances should they be kept with other sucker-mouth catfish, cichlids (even small and non-predatory ones), or other algae-eater species. They clean plants of growths. The fish are quite sensitive to water parameters and their stability. They require very clean, nitrate-free water. They tolerate dissolved nitrogen compounds poorly.
Filtration should be strong, preferably through peat, and requires aeration and weekly water changes. They are also very sensitive to medications, especially those containing copper. Without algae to graze on, provided only with regular fish food, they will starve to death. Supplementing with steamed vegetables, especially the peel-on part of a cucumber, is desirable. Water temperature should not exceed 27°C. pH 5.8-7.5; dH 4-18°; T 20-25°C.
Identification: Zebra oto — Otocinclus cocama.
Otocinclus flexilis, hoppei, huaorani, macrospilus.
Hisonotus aky, leucofrenatus, maculipinnis, nigricauda, notatus, paulinus. 
