Siamese algae eater
Crossocheilus oblongus
easy careOverview
The Siamese algae eater (Crossocheilus oblongus), or SAE, has a real claim to fame: it is one of the very few fish that will actually eat black beard algae, the tough, stubborn algae most fish ignore. Add its appetite for other soft algae and its peaceful, active nature and you have a genuinely useful community fish. The catch is identification — several lookalikes are sold under the same name — and the fact that it grazes algae most eagerly while young and hungry.
Tank & water
An active fish reaching 12–15 cm, the SAE needs at least 110 litres (30 gallons) with swimming room. Keep 24–28 °C with a good filter, decent flow and stable water.
- Swimming space and hides: open water to cruise plus plants and driftwood for cover.
- A secure lid: SAEs are strong swimmers and can jump.
- Balance, not miracles: an SAE helps, but algae is driven by light and nutrients — read how to get rid of aquarium algae.
Feeding
The SAE is an omnivore that eats algae readily when young but needs a full diet too. Offer sinking pellets, wafers, blanched vegetables and the occasional frozen treat. Don’t overfeed, or it will graze less algae. See the fish food hub and our best fish food picks. A slightly hungry young SAE is your best algae worker.
Tankmates
Peaceful and active, the SAE suits robust communities — tetras, rasboras, barbs, gouramis, corydoras and other algae-eaters like the bristlenose pleco and otocinclus. Older SAEs can get a little boisterous, so avoid very timid or long-finned fish. They generally leave adult cherry shrimp alone.
Frequently asked questions
The Siamese algae eater is the go-to fish for black beard algae — peaceful, active and hardworking. Buy the true species, keep it a touch hungry, and it will earn its place in a mid-sized community tank.
Siamese algae eater — frequently asked questions
Does the Siamese algae eater really eat black beard algae?
Yes — this is its claim to fame. The true Siamese algae eater is one of the few fish that will actually eat black beard algae, along with other soft algae types. It works best when young and hungry; well-fed adults graze algae less as they mature.
How do I tell a true Siamese algae eater from lookalikes?
Look for a single bold black stripe running from the snout right into the tail fin, with a clean, torpedo-shaped body. Lookalikes (flying foxes and false SAEs) have extra colour, gold above the stripe, or a stripe that stops before the tail. Only the true SAE reliably eats black beard algae.
How big does a Siamese algae eater get?
Around 12–15 cm and quite active, so it needs a tank of at least 110 litres with swimming room. It stays far smaller than a common pleco, but it is still a proper mid-sized fish rather than a nano species.
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