Siamese algae eater

Quick facts

Adult size

14 cm

Lifespan

can live up to 10 years

Tank zone

all

Temperament

peaceful

Difficulty

intermediate

Schooling

recommended 5+ (critical minimum 1, thrives at 8+)

Water parameters

Temperature

22–28°C

pH

6.0 to 7.5

Hardness

2 to 15 dGH

Tank requirements

Minimum volume

150 L

Minimum length

90 cm

Flow

moderate

Lighting

moderate

Substrate

any

Driftwood

preferred

Open swimming room

needed

Lid

required - jumper

Feeding

Diet: omnivore, feeds primarily at the all.

Eats black beard algae, hair algae, and other filamentous algae that most fish ignore. This is the main reason people buy them. However: SAEs become lazier about eating algae as they age and grow, especially if they have access to easier food. An SAE that's fed sinking pellets every day will stop bothering with tough BBA. Some keepers recommend underfeeding to maintain algae-eating motivation, but this should be done carefully. Supplement with blanched vegetables and algae wafers. SAEs also eat flatworms (planaria) and hydra, which is a useful bonus.

Vegetable matter required (algae wafers, blanched zucchini, spinach).

Compatibility

• Generally peaceful but becomes more boisterous with age. Juveniles are calm; adults can be pushy toward slow-moving bottom-dwellers.
• Fast swimmer that may stress timid tankmates with constant activity.
• Occasionally chases other SAEs and similarly-shaped fish. Territorial behavior increases with size.
• Works well in planted tanks with robust tankmates: tetras, barbs, rainbowfish, corydoras.
• May eat moss (java moss, christmas moss) if hungry. Not reliably plant-safe in all situations.

Habitat

Native to flowing streams in Thailand and the Malay peninsula. The true Siamese algae eater (Crossocheilus oblongus) is one of the few fish that eats black beard algae (BBA), which makes it highly valued in planted tank circles. Often confused with the Chinese algae eater (Gyrinocheilus aymonieri) and the flying fox (Epalzeorhynchos kalopterus), both of which are less useful and more aggressive. The distinguishing feature is the black horizontal stripe that extends into the tail fin and has a ragged (not smooth) upper edge. Reaches 15 cm and is an active swimmer that needs a 200 L tank as an adult.

Breeding

Not bred in captivity. All SAEs in the trade are wild-caught. No successful hobby breeding has been documented. The reproductive biology in the wild is poorly understood. This is one of the few popular aquarium fish with zero breeding information available.

Common problems

Misidentification is the biggest issue. Chinese algae eaters and flying foxes are frequently sold as SAEs, and they don't eat BBA. Learn the visual differences before buying. SAEs jump; a tight lid is mandatory. As SAEs grow past 10 cm, they become less interested in algae and more disruptive in the tank. Some keepers rehome them at this point. They're not aggressive enough to cause damage but their constant swimming and size can dominate a smaller tank. Lifespan is 8-10 years, which is longer than most people expect from an "algae eater" purchase.

Bioload

Bioload coefficient: 3.0 (active mid-size shoaler; comparable to a medium plecostomus).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size