Siamese Algae Eater

Crossocheilus oblongus

Also known as: SAE, Siamese flying fox

Water Parameters

• Temperature: 23–28°C
• pH: 6–8
• Hardness (GH): 36–268 ppm (2–15 dGH)

Values above are general hardness (GH). For carbonate hardness (KH), the buffer that keeps pH stable, see the water parameters guide.

Care Summary

The most effective algae-eating fish commonly available, and the standard recommendation once black beard or thread algae has taken hold, which few other fish will touch. Hardy, active, and long-lived, it earns its keep as a juvenile but shifts toward prepared foods as it matures and grows to around 15cm, so it is best seen as part of a clean-up strategy rather than a permanent algae machine. The recurring problem is identification: at least three similar fish are sold under overlapping names, and only the true Crossocheilus reliably does the job. The clearest tell is the black lateral stripe that continues into the tail, on a clear (not red-finned or gold-banded) body. Best in a roomy, well-oxygenated community with some current. Genuinely useful where it is correctly identified and not relied on alone.

Tankmates

Peaceful, fast, and busy: an excellent member of most active community tanks and one of the few fish that reliably eats black beard algae. Best kept either singly or in a group of five or more; in groups of two or three a pecking order forms and the dominant fish bullies the rest. Their speed and constant motion can unsettle slow, long-finned fish like bettas. The critical issue is buying the right fish: the true Siamese algae eater is routinely mixed up with the flying fox and the false siamensis (which eat less algae) and with the Chinese algae eater (a different, larger, increasingly aggressive species). Look for a single unbroken black stripe running into the tail fin and a body without a contrasting gold band.

Compatible with

• Harlequin Rasbora
• Zebra Danio
• Tiger Barb
• Gold Barb
• Congo Tetra
• Bronze Corydoras
• Bristlenose Pleco
• Boeseman's Rainbowfish

Avoid keeping with

• Betta
• Large Cichlids
• Aggressive Tankmates

Common Problems

• being confused with flying fox or Chinese algae eater at purchase
• reduced algae-eating and need for supplementary food as adults
• squabbling in groups of two or three
• outgrowing small tanks (reaches around 15cm)

Sources: seriouslyfish.com, fishbase.org · Last updated: 2026-06-20