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title: "Siamese Algae Eater: The Complete Care & Algae-Control Guide" description: "The definitive Siamese algae eater (Crossocheilus oblongus) care guide: the fish that eats black beard algae, true SAE vs flying fox ID, tank setup, diet, and tank mates." slug: siamese-algae-eater commonName: Siamese Algae Eater scientificName: Crossocheilus oblongus family: Cyprinidae order: Cypriniformes difficulty: Beginner minTankSize: 29 temperature: "75–81°F (24–27°C)" ph: "6.5–7.5" hardness: "5–18 dGH" lifespan: "8–10 years" maxSize: "6 inches (15 cm)" origin: "Thailand, Malaysia, Indonesia" publishedAt: "2026-06-04"

Siamese Algae Eater: The Complete Care & Algae-Control Guide

The Siamese algae eater is the most effective algae-eating fish in the freshwater hobby — and the only one that reliably eats the dreaded black beard algae that defeats most cleanup crews. An active, hardy, peaceful, torpedo-shaped fish, Crossocheilus oblongus is a workhorse that grazes black beard, hair algae, and biofilm tirelessly. The catch is that it's constantly confused with two cheaper look-alikes — the flying fox and the "false SAE" — that don't do the job, so knowing how to identify a true SAE is half the battle.

This guide is the complete reference: the SAE's biology and unmatched algae-eating, how to tell a true SAE from its imposters, how to set up its tank, what to feed it, why it grows large and needs a group, and which tank mates suit it.

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Species Overview

The Siamese algae eater (Crossocheilus oblongus, also seen as C. siamensis) is an active cyprinid from Southeast Asia, reaching about 15 cm (6 inches). It's a slender, silver-bodied, torpedo-shaped fish with a single bold black stripe running from the snout through to the tail, where the stripe has a slightly ragged or zig-zag lower edge — a key ID feature. Its fins are clear/colourless, and it has small barbels.

The SAE is the gold-standard algae-eating fish, uniquely valued because it's one of the very few fish that reliably eats black beard algae (BBA) as well as hair algae, biofilm, and leftover food. It's hardy, active, peaceful, and long-lived (8–10 years). It's rated beginner-friendly on care, but two things matter: it grows large and active (needing a reasonable tank), and you must buy the true SAE, not its lookalikes. Given a proper tank, it's one of the most useful and rewarding utility fish in the hobby.

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Natural History and Origin

Crossocheilus oblongus lives in fast-flowing, oxygen-rich streams and rivers of Thailand, Malaysia, Indonesia, and surrounding Southeast Asia, over rocks and submerged wood. This active-stream habitat gives it its energy, its love of swimming room and flow, and its grazing lifestyle — in the wild it rasps algae and biofilm from rocks and surfaces in moving water.

In the wild and the aquarium, SAEs are constant grazers, and crucially their algae-eating includes the tough, dark black beard algae (a red alga, Rhodophyta) that most fish ignore — making them invaluable for keepers battling BBA. They're social, often found in groups, and they remain active and somewhat shoaling in captivity. Note that their algae-eating appetite tends to decline with age and size — older, larger SAEs eat less algae and more prepared food, and may become a bit territorial — so they're most effective as algae controllers when young and kept slightly hungry.

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True SAE vs Flying Fox vs False SAE

This is the most important practical knowledge for buying one, because the look-alikes don't eat black beard algae and some grow aggressive.

The quick tells for a true SAE: a single black stripe that extends into the tail, with a zig-zag lower edge, clear fins, and no gold stripe. If there's a gold stripe above the black, or coloured fins, it's a flying fox — not the algae-eater you want. Buying the wrong fish is the most common SAE mistake.

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Water Parameters

SAEs are hardy and adaptable, doing well across a range of conditions, which makes them easy on the care side. They appreciate clean, well-oxygenated water with some flow, reflecting their stream origins. Confirm cycling with the nitrogen cycle tracker and check values with the water parameters reference. Good water and flow keep them active and grazing.

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Tank Setup Guide

Tank size

Because they reach 15 cm and are very active, SAEs need a minimum of 29 gallons (110 litres), with 40+ gallons better, and length matters for their swimming. They're often bought small for a planted tank's BBA problem, then outgrow nano setups — plan for the adult size. They do best as a small group (or singly in smaller tanks, since older SAEs can squabble).

Aquascape — planted with swimming room and flow

SAEs suit a planted tank with open swimming space, flow, and surfaces to graze — driftwood, rocks, and plants all grow the algae and biofilm they eat. They're generally plant-safe (they graze algae, not healthy plants, though a very hungry SAE may rasp soft new growth). Good flow and oxygenation reflect their stream origins and keep them active. A planted tank with a BBA or hair-algae problem is exactly where an SAE earns its keep.

Filtration, flow, lid

Use reliable filtration with moderate flow and good oxygenation. A secure lid is important — SAEs are active fish and known jumpers. Clean, flowing, well-oxygenated water keeps them grazing and healthy.

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Feeding Guide — Keep Them Hungry for Algae

The SAE's value is its algae-eating, and the trick to maximising it is not overfeeding prepared foods, so the fish stays motivated to graze algae.

What to feed

• Algae in the tank — black beard algae, hair algae, soft green algae, and biofilm; their primary and most valuable food, especially when young.
• Algae wafers and vegetable-based foods — supplements, fed sparingly so they keep grazing algae.
• Blanched vegetables — zucchini, cucumber, spinach for variety.
• Occasional protein — they're omnivores and take pellets, flake, and small frozen foods; keep this modest so they don't lose interest in algae.

How often

Feed sparingly — once daily or even less of prepared food in an algae-rich tank, so the SAE keeps eating algae rather than waiting for handouts. Overfeeding is the main reason SAEs "stop eating algae." That said, in a clean tank with little algae, you must feed them properly to avoid starvation — balance is key. Older, larger SAEs naturally eat more prepared food and less algae, which is normal.

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Behavior and Temperament

Siamese algae eaters are active, peaceful, and busy — they're constantly on the move, grazing surfaces, swimming in the current, and resting on broad leaves and wood. Young SAEs are sociable and can be kept in a small group; older, larger SAEs can become mildly territorial toward each other and similar fish, so in smaller tanks a single SAE is often best, while larger tanks can host a small group.

They're peaceful toward other species and make excellent, hard-working community members. Their energy means they suit active community tanks rather than ultra-calm nano setups. The main behavioural notes are their activity and adult size (plan the tank accordingly) and the mild territoriality of old individuals. As utility fish, they're unmatched — few fish combine such effective algae control with such a peaceful, hardy nature.

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Compatibility

SAEs are excellent peaceful community fish that suit active, robust tanks.

Good tank mates: tiger barb, denison barb, boesemani rainbowfish, congo tetra, clown loach, bristlenose pleco, corydoras, larger peaceful tetras and rasboras, and most active community fish.

Cautions:

• Very small shy nano fish — may be disturbed by the SAE's energy (though it won't prey on them).
• Other SAEs in small tanks — older individuals can squabble; keep one, or a group in a large tank.
• Long-finned slow fish — a hungry SAE may occasionally rasp at slime coats or fins of very slow fish (uncommon but possible).

Use the compatibility checker. SAEs pair well with active community fish and are a natural addition to any planted tank with an algae problem.

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Breeding Guide

Siamese algae eaters are not bred in home aquaria — commercial supply comes from farms in Southeast Asia that use hormone induction to spawn them, much like many barbs and "sharks." Their natural breeding involves flowing-water spawning that's impractical to replicate at home, and sexing them is difficult outside of breeding condition (females may be slightly rounder).

For keepers, the SAE is a utility and display fish to enjoy rather than breed. The reliance on farm production is also a reason to buy from reputable sources, both to get true SAEs and to avoid mislabelled look-alikes.

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Health and Disease

Siamese algae eaters are hardy, and disease is uncommon with good care.

Ich can follow temperature swings or stress; treat promptly (mindful that, like many scaleless-leaning cyprinids, they appreciate careful dosing). Bacterial and fungal infections follow poor water or injury. Jumping is a leading non-disease cause of loss — keep a secure lid. Starvation can occur if a clean tank has little algae and they're underfed — provide proper food in low-algae tanks. As active, oxygen-loving fish, they need clean, well-oxygenated water.

Prevention: a stable, cycled, well-oxygenated tank with flow and grazing surfaces, appropriate (adult) tank size, a secure lid, balanced feeding (sparing prepared food in algae-rich tanks, proper food in clean ones), and quarantine of new arrivals. Given those, SAEs are robust, long-lived, hard-working fish.

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Interesting Facts

• The black-beard-algae fish. The SAE is one of the only fish that reliably eats black beard algae — its claim to fame and the reason keepers seek it out.
• A field of imposters. It's routinely confused with the flying fox and "false SAE"; the true SAE's stripe runs into the tail with clear fins and no gold stripe.
• Appetite fades with age. Older, larger SAEs eat less algae and more prepared food and can grow mildly territorial — they're most effective young and kept hungry.
• Farm-bred via hormones. Not bred at home; commercial fish are hormone-induced on farms, so buy from reputable sources to get the real thing.
• A stream athlete. From fast Southeast Asian streams, it's active and loves flow and oxygen — and it jumps, so keep a lid.

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Bringing It Together

The Siamese algae eater is the most effective algae-eating fish you can keep — the rare fish that actually eats black beard algae — and a hardy, peaceful, long-lived community workhorse. The two keys to success are buying the true SAE (stripe running into the tail, clear fins, no gold stripe — not a flying fox), and giving it a tank that fits its adult size and activity (29 gallons-plus with flow and a lid). Keep its prepared feeding sparing so it stays motivated to graze algae, pair it with active community fish, and it will tirelessly clear BBA and hair algae from your planted tank for years. For the soft green algae and diatoms the SAE is less focused on, pair it with an otocinclus group or a bristlenose pleco. Plan the build with the AI Tank Blueprint generator, and read up on fixing the root cause of black beard algae alongside adding an SAE.