Description
The Siamese algae eater is an elongated, silvery cyprinid with a black stripe running from snout to tail. Its fame comes from something specific: it is one of the few fish that eats black beard algae, the pest almost nothing else touches.
Two things are worth knowing before buying it. First, it grows fairly large — about 15 cm — and is very active, so it is not a nano tank fish. Second, in shops it is often confused with relatives that do not eat algae, such as the more territorial flying fox. In the true species the black stripe runs right to the end of the tail.
With age it eats more fish food and less algae. It stays useful, but it is not a permanent fix for an algae problem.
Behavior
Peaceful towards other species and somewhat quarrelsome with its own: adults chase each other. A single fish, or a group of three or more in a large tank, works; two tend to fight.
It lives well with tetras, rasboras, barbs, gouramis, corydoras and peaceful cichlids.
Avoid housing it with very slow or shy fish whose food it steals, and small tanks where its activity stresses everyone.
Habitat
Crossocheilus oblongus lives in Southeast Asian rivers — the Mekong and Chao Phraya basins, the Malay Peninsula and the Sunda Islands — in flowing stretches with stone and gravel bottoms and algae-covered submerged logs.
In the aquarium it needs swimming room, some flow and stones or wood to graze. And a lid, because it jumps.
Details
🌊 Water parameters
🐠 Minimum tank size
Breeding
It does not breed in home aquariums. Fish in the trade come from farms that use hormone induction.
Sexing is difficult: adult females are somewhat stockier.
Diet
An omnivore with a large plant component.
- Staple: spirulina tablets or sinking plant-based food.
- Vegetables: blanched courgette or cucumber.
- Supplement: some frozen food.
If you want it to keep eating algae, do not overfeed it: an algae eater full of pellets has no reason to graze.
What about your tank?
Enter your tank's values to see only the compatible species that fit them. Litres apply to fish.
Compatible fish
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–8 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–25 °C.
They share water: pH 6.5–7.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5–8 and 24–26 °C.
They share water: pH 6.5–7.5 and 25–26 °C.
They share water: pH 6.5–8 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 7.5–8 and 24–26 °C.
They share water: pH 7.5–8 and 24–26 °C.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7.2 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5–7 and 26 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5 and 24–26 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 7–8 and 24–26 °C.
Compatible invertebrates
General guidance based on water parameters, behaviour and known exceptions; always review the individual animals' and aquarium's specific needs.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 7–8 and 24–25 °C.
They share water: pH 7.5–8 and 24–26 °C.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–6.8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–6.8 and 24 °C. They only meet at the very edge, so the tank has to hold that value.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 6.5–7.5 and 24–26 °C.
They share water: pH 7–8 and 24–26 °C.
They share water: pH 6.5–8 and 24–26 °C.
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They share water: pH 7–8 and 24–26 °C.
Sources
- FishBaseFroese, R. and D. Pauly. Editors. 2026. FishBase. World Wide Web electronic publication.
Seriously Fish has no page for this species; the parameters come from FishBase alone.
Plan your next aquarium
Is this fish right for you? Plan a suitable aquarium before setting it up.