FishFreshwaterIntermediate
Chinese Algae Eater (CAE)
Gyrinocheilus aymonieri
Probably the most misrepresented fish in the hobby. Sold at 3 cm (1 inch) as an excellent scavenger, it rapidly transforms into a frighteningly aggressive 28 cm (11 inch) torpedo, notorious for sucking the slime coat off other fish.
Water Temperature
22 - 28 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Bottom
Adult size
25 cm
Minimum tank volume
>= 300 L
Minimum group
>= 1
GH
5 - 15 dGH
KH
2 - 7 dKH
TDS
95 - 295 ppm
Conductivity
148 - 461 uS/cm
Species description
Geographical Origin and Habitat: Asia (Thailand, Mekong basin, Chao Phraya river). River streams with moderate to strong current, full of smooth sun-kissed rocks and bare trunks.
Taxonomy and Morphology: Chinese Algae Eater - CAE (Gyrinocheilus aymonieri). Asian sucker fish, actually NOT Chinese but Thai. Huge and highly effective sucker mouth under the snout, which it uses to resist rapids.
Social Behavior: Dr. Jekyll and Mr. Hyde. When very young (5-6 cm / 2 inches) they are tireless peaceful workers. Becoming adults (over 15 cm / 6 inches) they turn into "psychopathic killers", extremely territorial and aggressive even with their own kind.
Coloration and Sexual Dimorphism: The wild form has an olive-gray back with a black zigzag line along the flank (mesh-like). In stores, 95% is sold in the "Gold" variant, completely lemon yellow or faded orange. Females are mastodontic.
Care, breeding and tankmates
Aquarium Setup: Due to their adult size they need sturdy tanks (150 cm / 60 inches). Large smooth river rocks to cling to for rest, powerful filters with strong jets and caves to define their territorial boundaries.
Diet and Feeding: Juveniles: avid algivores, they clean the glass in hours. Adults: they switch to a 100% carnivorous/protein diet, refusing algae and stealing food (granules, tubifex) from any other fish by headbutting them.
Water Quality: Not delicate on parameters (tolerates soft and hard waters), but needs high oxygenation. Poor maintenance pushes its territorial nature to historic highs of violence.
Compatibility and Cohabitation: The worst community tankmate. Reaching maturity, it uses its sucker mouth to attach itself to the flanks of slow fish (Angelfish, Discus, Orandas), literally sucking their mucus and skin (causing ulcerations and death). Can only cohabit with large and fast Barbs (e.g. Tiger Barbs).
Aquarium Breeding: Never reproduced in home aquariums. In Asian farms (where the Golden forms are obtained) huge tanks with mass hormonal injections are used to force spawning.
Risks and Diseases: The purchasing mistake par excellence. Thousands of aquarists buy it as a cute little 4 cm (1.5 inch) "glass cleaner" for a 30 liter (8 gallon) tank, only to find themselves with a 25 cm (10 inch) yellow monster that kills Corydoras and flays goldfish.
Geographic Origin and Distribution
Asia (Thailand, Mekong basin, Chao Phraya river). River streams with moderate to strong current, full of smooth sun-kissed rocks and bare trunks.
Origin
South and Southeast Asia
Fish profile
- Temperament
- Semi-aggressive
- The temperament of the Chinese Algae Eater is infamous in the aquarium hobby for its Dr. Jekyll and Mr. Hyde transformation. While young specimens are peaceful, industrious algae eaters, adults become highly territorial, aggressive, and disruptive. They are strongly disliked by many aquarists because adult specimens frequently attack and latch onto the sides of other fish to consume their nutritious slime coat. They are completely intolerant of their own kind and will fiercely defend their chosen hiding spots from any intruders. They should only be kept by experienced aquarists who understand their complex and challenging adult behavior.
- Diet
- Omnivore
- In their youth, they are ravenous herbivores that enthusiastically consume soft green algae, diatoms, and biofilm from aquarium surfaces. As they grow older and larger, their dietary preference shifts dramatically towards a more omnivorous, protein-rich diet, and they will largely ignore algae. To keep adults healthy and deter them from sucking on tank mates, they must be fed sinking wafers, high-quality pellets, and meaty foods like bloodworms and brine shrimp. They will still appreciate blanched vegetables like zucchini or cucumber. Providing a varied, protein-inclusive diet is essential for mitigating their aggressive tendencies.
- Life expectancy
- 10-15 years
- In optimal aquarium conditions, Gyrinocheilus aymonieri boasts a remarkable lifespan, commonly ranging between 10 and 15 years. The longevity of this fish is highly dependent on the available space, as its continuous growth demands large tanks and excellent filtration. Improper nitrate management and inadequate nutrition during its adult phase can significantly shorten this lifespan. A stable environment with controlled chemical parameters is key to ensuring its long-term survival.
- Adult size
- 25 cm
- The catalog's scalar value is 25 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 28 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Gyrinocheilus aymonieri (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Solitary
- There are no obvious external sexual differences between males and females, making sexing them visually almost impossible. Due to their extreme territoriality and intraspecific aggression as adults, keeping more than one in an aquarium is highly discouraged unless the tank is exceptionally large (over 100 gallons). Attempting to establish a sex ratio or keeping a group will inevitably lead to dominant individuals harassing the weaker ones, often to the point of death. They do not form pairs or social bonds. A single specimen is the only safe recommendation for the vast majority of aquariums.
- Feeding frequency
- Twice daily
- Juveniles constantly graze on algae throughout the day and rarely need supplemental feeding if the tank has sufficient algal growth. However, adult Chinese Algae Eaters should be fed once or twice a day with sinking, protein-rich foods to keep them satiated. They are fast, aggressive eaters that can easily outcompete slower bottom-dwellers like Corydoras for food. It is important to ensure that food reaches the bottom without being intercepted by mid-water fish. Overfeeding should be avoided to maintain water quality, but underfeeding an adult will almost certainly lead to it attacking other fish for their slime coat.
- Bioload
- The Chinese Algae Eater produces a moderate to high bioload, especially as it matures and reaches its substantial adult size of up to ten inches. While they are highly efficient algae grazers as juveniles, their overall waste production increases as their diet shifts toward meatier foods in adulthood. A robust biological and mechanical filtration system is necessary to handle the detritus they produce and stir up from the substrate. Regular vacuuming of the gravel and consistent water changes are crucial to prevent the buildup of nitrates and maintain a healthy environment. They are quite hardy, but poor water quality will significantly shorten their lifespan.
- Flow
- Stagnant
- They originate from fast-flowing rivers and streams in Southeast Asia, so they highly prefer an aquarium with strong water currents and high oxygenation. The use of powerheads, wavemakers, or a strong canister filter outflow is highly recommended to replicate their natural riverine environment. They use their specialized sucker mouths to cling tightly to rocks and smooth surfaces, resisting the strong current with ease. While they enjoy the flow, providing sheltered areas behind driftwood or large rocks allows them to rest. Poorly oxygenated or stagnant water will cause them severe stress and lethargy.
- Reproduction
- Oviparous
- Breeding the Chinese Algae Eater in a home aquarium is considered exceptionally rare and incredibly difficult to achieve. In commercial settings, they are bred in massive outdoor ponds using hormone injections to induce spawning, a process that cannot be replicated by the average hobbyist. They are egg-layers, but the specific environmental triggers—likely related to seasonal monsoon floods and massive water parameter shifts—are not fully understood. Furthermore, their extreme aggression toward conspecifics makes establishing a compatible breeding pair nearly impossible in confined spaces. Therefore, almost all specimens sold are commercially farmed.
- Compatibility & tankmates
- As juveniles, they are generally peaceful and excellent algae cleaners that can be kept in most community tanks. However, as they mature, their temperament undergoes a drastic change, becoming highly territorial and aggressively intolerant of tank mates. They are notorious for developing a taste for the slime coats of slow-moving, flat-sided fish like Discus, Angelfish, and Severums, often leaving circular lesions that easily become infected. Adult specimens are best kept with fast-moving, robust fish such as large barbs, loaches, or aggressive cichlids that can defend themselves. Keeping more than one in the same tank usually results in severe intraspecific violence.
- Tank level
- Bottom
- They are primarily bottom-dwelling fish that spend the majority of their time attached to rocks, driftwood, or the aquarium glass. They are highly active and will frequently dart along the substrate or zip up the glass to graze on biofilm. An aquascape with smooth river rocks, sturdy driftwood, and broad-leaved plants provides ideal surfaces for them to cling to and defend. They rarely swim freely in the mid-water or upper levels unless darting to the surface for a quick gulp of air or grabbing sinking food. Providing plenty of caves and hiding spots is essential for their security.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.5 ± 0.25 se
- Phylogenetic uniqueness (PD50)
- 0.75
- Bayesian Length-Weight
- a = 0.00389, b = 3.12
- VulnerabilityLow vulnerability (24 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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