Siamese Algae Eater Care Guide

The Siamese algae eater is the genuine article for hair and black-beard algae — one of the very few aquarium fish that actually eats it — but two facts decide whether you get the right animal: it is a 15 cm carp, not a loach, and the shops are full of look-alikes that don't do the job.

Siamese Algae Eater at a glance

The sourced figures the welfare engine uses to judge Siamese Algae Eater — the parseable key facts.

Where it comes from

Despite the slender, barbeled, bottom-grazing "loach look," this is a cyprinid — Cyprinidae, subfamily Labeoninae, the carp and minnow family, a close relative of barbs and danios rather than of kuhli or clown loaches. It comes from clear, fast-flowing streams and tributaries across mainland and insular Southeast Asia (Borneo, Peninsular Malaysia, southern and western Thailand, and the Chao Phraya and Mekong basins), living over boulders, pebbles, gravel and sand among submerged wood and roots. It grazes aufwuchs there — algae, diatoms and phytoplankton, a near-pure microphage at trophic level 2.0 — which is exactly why it eats algae in the tank. The fast-stream origin explains the rest of the care: it wants well-oxygenated water with good flow, near-neutral and adaptable chemistry, and flat grazing and resting surfaces, because unlike a true mid-water cyprinid it cannot hover and must rest on wood, rock or broad leaves.

Did you know?

• It's not a loach — it's a carp. Despite the slender, barbeled, bottom-grazing look, the SAE is a cyprinid, a close relative of barbs and danios, not of kuhli or clown loaches.
• One of the only fish that eats black-beard algae: Wikipedia calls it the only known fish to consume red algae including black brush or beard algae, and Seriously Fish the most efficient BBA consumer of its group. This is its entire reputation.
• Nobody can fully agree what species it is. FishBase keeps C. oblongus valid, while Seriously Fish argues the true hobby fish is C. langei and that C. oblongus "is almost certainly not the SAE in the aquarium hobby."
• Its name-stealing twin: FishBase's official common name for C. oblongus is "Siamese flying fox" — almost identical to the Flying Fox it is most confused with, which itself fuels the shop mix-ups.
• The most reliable field mark is the tail: on the true SAE the black stripe runs all the way into the caudal fin, while on the Flying Fox and false siamensis it stops where the tail begins.

Tank size — and why

The engine's 30 gallons is on the low side. Quick-guides quote 20 gallons for one, but Aquarium Co-Op recommends a 50-55 gallon tank even for a single fish, and Seriously Fish specifies a 150 by 45 cm footprint for a group — a 4-5 ft, 120-gallon-plus tank. The driver is not bioload but adult size and behaviour: this is a fast, restless 15 cm grazer that turns territorial with age, so it needs floor area and length for the group to spread out and so the dominant fish cannot corner the subordinates. Prioritise a long footprint over a tall one, and treat a nano "cleanup crew" slot as the wrong home entirely.

As a guide, a 30-gallon tank comfortably suits about 5–7 Siamese Algae Eater as a single-species display, leaving room for tankmates.

How big does it really get?

Full-grown Siamese Algae Eater reach about 15 cm (5.9 in) long, but they are usually sold at only about 3 cm (1.2 in) — a typical shop size (estimate). At full size, Siamese Algae Eater needs roughly a 30-gallon tank, about 76 cm long; a common 10-gallon starter kit is only about 51 cm.

Adult size is sourced; the shop size is a typical-juvenile estimate; tank length is approximate for a standard 30-gallon aquarium.

Water parameters in practice

A hardy, adaptable fish — far less chemistry-sensitive than the scaleless loaches it gets grouped with, and because it is fully scaled it is not subject to any half-dose medication rule. Aim for 24-26 C as the healthy target, with tolerance from the cool end (down to about 20 C, reflecting the flowing-stream origin) up to roughly 27 C; keep it well-aerated at the warm end, because this is an oxygen-loving stream fish and warm water holds less oxygen. pH is near-neutral and forgiving across 6.0-8.0, soft to hard water, so no acidification or blackwater botanicals are needed. Stability and good oxygenation matter more than chasing an exact number; give it a cycled tank with strong flow, around 4-5 times turnover per hour and good surface agitation.

Will it thrive in your water?

The comfortable range for Siamese Algae Eater is about 22–26 °C (72–79 °F) and pH 6–8. Test your own tap water against it below.

These are the sourced comfortable ranges. Stable water matters more than chasing an exact number — a steady reading inside the band beats a "perfect" one that drifts. Some fish also need a particular water hardness (GH); where that applies, the prose above covers it.

Diet & feeding

In the tank it behaves as an omnivore, but its whole reputation rests on one rare trait: the true SAE is one of the very few fish that eats hair algae and black-beard or black-brush (BBA) algae — Seriously Fish calls it "the most efficient consumer of BBA" of its group, and Wikipedia rates it the only known fish to consume red algae including black brush. Two honest caveats: only the younger, softer growths may be taken, and appetite for algae fades with age and overfeeding — older, well-fed fish prefer prepared food and graze less. Keep it lean and vegetable-leaning to preserve the grazing behaviour. Offer a quality dried staple with added Spirulina, algae wafers and sinking pellets, plus blanched courgette and spinach, with only occasional protein. It is a fast, assertive feeder that out-competes slow tankmates, so feed small amounts once or twice daily and never stuff it — a full SAE stops working on algae. It is an aid to algae control, not a cure for a tank-wide outbreak driven by nutrients or CO2.

Gear & setup

Provide driftwood, rocks and broad-leaved or robust plants as grazing surfaces and, just as importantly, as line-of-sight breaks to defuse adult territoriality — Aquarium Co-Op specifically advises obstacles that block sightlines. Include flat resting surfaces, since the fish cannot hold itself in mid-water. Any standard substrate is fine; there is no barbel-protection sand mandate as with the scaleless loaches. Run strong, well-oxygenated flow (4-5 times turnover) and moderate-to-bright light, which also grows the algae it eats. A tight-fitting lid is mandatory — this is a confirmed jumper, especially when startled, newly introduced or stressed, so cover every gap and cut-out.

Temperament & behaviour

Peaceful as a juvenile and semi-aggressive or territorial with age. It is a shoaling rather than schooling fish that develops a distinct pecking order, and the aggression is intraspecific and age-linked rather than predatory — milder than its look-alikes, and notably less aggressive than the Chinese algae eater or red-tailed shark. It is diurnal and highly active, a fast grazer that roams and works every surface by day. The black lateral stripe doubles as a mood gauge: it pales when the fish is stressed or sparring but never changes width.

Group & social needs

Keep ONE, or keep a group of 5-6 or more — never a pair or trio, which is the worst possible outcome. In small numbers the dominant fish bullies the weaker individuals incessantly; a larger group dilutes the pecking order so no single fish is targeted, the same mechanism that governs yoyo loaches. Seriously Fish recommends a group of six or more for exactly this reason.

Compatible tank mates (preview)

A short, engine-cleared shortlist — the species TankStocking's welfare engine clears with Siamese Algae Eater and that suit its size and temperament best. Tap a name for its care guide, or use + to load the pairing in the planner.

• Boesemani Rainbowfish+Peaceful temperament, similar adult size
• Bolivian Ram+Peaceful temperament, similar adult size
• Brilliant Rasbora+Peaceful temperament, similar adult size
• Bristlenose Pleco+Peaceful temperament, similar adult size
• Clown Pleco+Peaceful temperament, similar adult size
• Congo Tetra+Peaceful temperament, similar adult size
• Dwarf Gourami+Peaceful temperament, similar adult size
• Gold Barb+Peaceful temperament, similar adult size

This engine-cleared shortlist is Siamese Algae Eater's tankmate surface for now — a dedicated tank-mates guide can follow for high-demand species.

Breeding & sexing

Effectively not achievable in the home aquarium — reproduction is not thought to have occurred in the hobby. Natural spawning is tied to seasonal and flow cues that cannot be replicated in a tank, so commercial stock is farm-produced in Southeast Asia, commonly hormone-induced, which is also part of why mislabeled look-alikes enter the trade. Sexing is subtle and reliable only in mature fish, where females are thicker-bodied than males; young fish cannot be sexed externally.

Lifespan

Around 8-10 years with good care, and over 10 in optimal conditions; lower "4-5 year" figures generally reflect under-fed or poorly-housed fish. What shortens it: chronic poor or unstable water, sustained high temperature with low oxygen (a stream fish kept too hot and still), the stress of being bullied in a pair or trio, jumping from an uncovered tank, and the extremes of starvation or obesity.

Common mistakes

• Buying the wrong fish. The number-one SAE mistake is bringing home a Flying Fox (won't reliably eat BBA), a false siamensis (Garra, poor algae eater), or a Chinese algae eater (aggressive, reaches ~28 cm, rasps slime coats). The tells for the true SAE: a ragged black stripe running all the way into the tail fin, clear fins, no gold stripe, one small barbel pair, no flaps at the mouth corners, and no sucker mouth.
• Treating it as a loach. It is a cyprinid; it is fully scaled, takes normal medication doses, and is grouped wrongly under "Loaches" in many references.
• Keeping a pair or a trio — the worst social outcome, where the dominant fish relentlessly bullies the subordinates. Keep one, or 5-6+.
• Underestimating adult size and activity. It reaches ~15 cm and is fast and busy; plan a 50-55 gallon-plus tank with a long footprint, not a nano cleanup slot.
• No lid. It is a jumper, and an open or gappy tank loses the fish.
• Expecting a permanent algae cure. It eats hair and BBA well when young and slightly hungry, but older or overfed fish graze less and it cannot fix the underlying nutrient or CO2 imbalance.
• Putting it in a dedicated dwarf-shrimp breeding tank. Adult shrimp and snails are generally fine, but shrimplets may be picked off by this opportunistic omnivore.

Signs of trouble

• A faded or pale lateral stripe — the built-in stress gauge, signalling bullying, poor water or fright.
• Gasping at the surface — heat or low oxygen in a fish that needs well-aerated water.
• Hiding and refusing to graze, loss of condition — often a bullied subordinate in a too-small group.
• Clamped fins and listlessness — general stress; check temperature stability, oxygen and water quality first.

Is this fish right for you?

Don't buy an SAE if you cannot confidently ID the true fish in the shop — stock is commercially farmed and frequently mislabeled, so inspect each fish for the ragged stripe into the tail, clear fins, single barbel pair and the absence of lip flaps or a sucker mouth, and don't trust the tank label. Skip it if you only have a small or nano tank, if you want exactly two or three of them, if you expect a guaranteed algae cure with no diet management, or if you keep a breeding dwarf-shrimp colony you can't risk. There are no legitimate dyed or balloon morphs — any "variety" is really a look-alike species or the unresolved oblongus/langei complex — so there is no morph ethics red flag, but quarantine farmed stock, which can carry disease.

Bringing one home

Add it to a cycled, mature, well-oxygenated tank with established algae and grazing surfaces so it has something to work from day one, and keep the lid sealed — newly introduced fish are most prone to jumping in the first day or two. Quarantine farmed stock, which can carry disease; as a fully scaled cyprinid it tolerates normal medication doses, unlike the scaleless loaches.

Common questions

Is the Siamese algae eater a loach?

No. It is a cyprinid — the carp and minnow family, the same as barbs and danios — not a loach. The "loach look" is superficial. Practically it matters: it is fully scaled and takes normal medication doses.

How do I tell a true SAE from a Flying Fox or Chinese algae eater?

True SAE: a ragged black stripe running all the way into the tail fin, clear colourless fins, no gold stripe, one small barbel pair, no mouth-corner flaps and no sucker mouth. The Flying Fox has a gold stripe and coloured fins and the stripe stops at the tail; the Chinese algae eater has a sucker mouth, grows to ~28 cm and turns aggressive.

Does it really eat black-beard and hair algae?

Yes — it is one of the very few fish that genuinely eats hair and black-beard (BBA) algae. The caveats: it prefers softer young growth, and appetite fades with age and overfeeding, so keep it lean. It is an aid, not a cure for an outbreak.

How many should I keep — one or a group?

Keep ONE, or a group of 5-6 or more. Never a pair or trio: in small numbers the dominant fish bullies the others incessantly, while a bigger group spreads the pecking order so no single fish is targeted.

How big does it get and what tank size does it need?

About 15-16 cm, reached in roughly two years. The engine's 30 gallons is low for a fast, territorial-with-age fish; 50-55 gallons (a 4 ft-plus footprint) is the better floor, especially for a group.

Is it safe with shrimp and snails?

Largely yes — unlike the clown and dojo loaches it leaves snails and adult or larger shrimp alone, so it is genuinely invert-safe. The one caution is a dedicated dwarf-shrimp breeding tank, where shrimplets may be picked off.

Sources & confidence

Sources & confidence (9 species)

These back the Siamese Algae Eater figures and the previewed tank mates above. Each figure is read from the TankStocking species database (v2026.06); below is the care reference behind it and how confident we are in that data. Confidence reflects the source quality, not whether any pairing is safe. Full source list and the welfare model are on the methodology page.

• Siamese Algae Eater Crossocheilus oblongus — Seriously Fish — Crossocheilus langei / SAE; Aquarium Co-Op SAE care (https://www.seriouslyfish.com/species/crossocheilus-langei/) medium confidence
• Boesemani Rainbowfish Melanotaenia boesemani — Seriously Fish; Aquarium Co-Op Boesemani guide high confidence
• Bolivian Ram Mikrogeophagus altispinosus — Seriously Fish (seriouslyfish.com/species/mikrogeophagus-altispinosus) high confidence
• Brilliant Rasbora Rasbora einthovenii — Seriously Fish (seriouslyfish.com/species/rasbora-einthovenii) high confidence
• Bristlenose Pleco Ancistrus sp. — Aquarium Source / aqua-fish.net Ancistrus care guides high confidence
• Clown Pleco Panaqolus maccus — Fish Laboratory (fishlaboratory.com/fish/clown-pleco); AquariumStoreDepot high confidence
• Congo Tetra Phenacogrammus interruptus — Seriously Fish (seriouslyfish.com/species/phenacogrammus-interruptus) high confidence
• Dwarf Gourami Trichogaster lalius — Seriously Fish (seriouslyfish.com/species/trichogaster-lalius) high confidence
• Gold Barb Barbodes semifasciolatus — Fishlore gold barb profile / FishBase Barbodes semifasciolatus high confidence

Care-guide sources (6)

This guide synthesises the references below; where they disagree, the range and the disagreement are noted in the text above. The figures in the key-facts box are read from the TankStocking species database (v2026.06). Full welfare model on the methodology page.

• Seriously Fish — Crossocheilus langei (SAE)
• FishBase — Crossocheilus oblongus
• Wikipedia — Siamese algae eater
• Aquarium Co-Op — Care Guide for Siamese Algae Eaters
• AquariumStoreDepot — Siamese Algae Eater: True vs. False SAE Guide
• Fishkeeping World — Siamese Algae Eater

More on Siamese Algae Eater

Related guides on TankStocking — each scored by the same welfare engine as the planner.

This care guide is a sourced planning reference, not veterinary advice — individual fish, filtration and maintenance all matter. Cycle the tank, test your water, and observe your fish. How TankStocking works →