Chinese Algae Eater (Gyrinocheilus aymonieri)

Gyrinocheilus aymonieri, the Chinese Algae Eater (somewhat misleadingly named — it originates from Southeast Asian mainland rivers, not China), is one of the most widely sold algae-eating fish in the aquarium trade. Its powerful sucker mouth, used to attach to rocks and surfaces while grazing algae, makes it an effective algae control tool in the right situation.

Juveniles are excellent algae eaters — peaceful, effective, and relatively unobtrusive. However, the Chinese Algae Eater has a significant and well-documented behavioural change as it matures: adults become increasingly territorial, particularly toward other Chinese Algae Eaters, and — more problematically — may begin to harass larger, flat-bodied fish such as Angelfish, Discus, and Goldfish, sucking on their slime coat. This change in behaviour has given the species a mixed reputation in the hobby.

In its natural habitat — the larger river systems of Thailand, Cambodia, Vietnam, and surrounding areas — it inhabits fast-flowing, rocky sections of rivers where it grazes periphyton from rocks using its unique sucker mouth. It can breathe while feeding by passing water through a second opening (spiracle) behind the gill opening rather than through the mouth.

The Chinese Algae Eater is the most suitable for large community aquariums with robust, similarly sized fish where its adult territorial behaviour is less problematic. It is a poor choice for planted nano tanks, tanks with discus or angelfish, or with any passive, flat-bodied fish.

Tank Setup: A minimum 150-litre aquarium for an adult. Provide smooth rocks, driftwood, and moderate water flow. Dense planting is optional. Good filtration. Provide hiding spots — territorial adults benefit from clearly defined cave territories.

Water Parameters: Temperature 24–28°C; pH 6.5–8.0; GH 5–20 °dH; KH 3–12 °dH. Adaptable to a wide range of conditions. Standard community aquarium water is suitable.

Feeding: Herbivore-detritivore when young; increasingly omnivorous as adults. Feed algae wafers, blanched vegetables, spirulina pellets, and occasional sinking carnivore pellets for adults. Do not rely solely on algae — supplement feeding ensures nutritional adequacy and reduces mucus-sucking from other fish.

Tank Mates: Best with other robust, active fish of similar or larger size: large barbs, medium to large tetras, robust cichlids, loaches. Avoid Angelfish, Discus, Goldfish, and all flat-bodied slow-moving fish that may be harassed.

Behaviour: Juveniles: peaceful, effective algae eaters. Adults: increasingly territorial toward conspecifics and may harass flat-bodied fish. Keep one per tank unless the tank is very large (300+ litres).

Health: Hardy and robust. Occasionally develops HLLE (head and lateral line erosion) from nutritional deficiency or poor water quality. Varied diet and regular water changes prevent this.