5 × Siamese Algae Eaters (Crossocheilus cf. langei)

This listing is for a group of 5 Siamese Algae Eaters listed as Crossocheilus cf. langei. The aquarium trade has used “Siamese algae eater” for several similar Crossocheilus. The “cf.” indicates a provisional identification: the fish is considered close to C. langei, but the exact species is not confirmed.

The current pack record lists the fish at approximately 3–3.5 cm supplied size. That juvenile size should not be confused with adult housing. FishBase records verified Crossocheilus langei to 14.5 cm total length, while UK Siamese-algae-eater guidance commonly plans around fish of roughly 14–16 cm. These are active river-type cyprinids that need long-term swimming room, oxygenation and deliberate feeding, not a small “clean-up crew” tank.

What you are buying

• Sale unit: 5 Siamese Algae Eaters
• Supplier/trade identity: Crossocheilus cf. langei
• Current supplied size: approximately 3–3.5 cm
• Verified species reference: FishBase records Crossocheilus langei to 14.5 cm total length
• Social plan: five matches the commonly used “one or five-plus” starting rule; a five-fish adult group needs substantially more usable space and biological capacity than one fish
• Adult housing screen: plan around a long aquarium, with 120 cm of swimming length as a minimum reference point for an individual; do not assume the same minimum is enough for five adults
• Temperature guidance: around 22–27°C for Siamese-algae-eater care
• pH guidance: about 6.0–8.0
• Water: clean, highly oxygenated, mature freshwater
• Diet: omnivore/periphyton grazer that still needs supplementary prepared food

Identity matters with “Siamese Algae Eater”

The common name is less precise than it sounds. Similar striped Crossocheilus species have circulated in the aquarium trade under overlapping names, and a dark side stripe by itself does not prove exact species.

Adult size and aquarium planning

These fish are often sold as small juveniles, which can make them look suitable for a modest aquarium. Plan for the adult group instead. FishBase records verified C. langei to 14.5 cm total length, and current UK Siamese-algae-eater guidance uses an aquarium at least 120 cm long for an individual.

A group of five is a different stocking problem from one fish. It needs more swimming space, more mature filter capacity, several feeding positions and enough visual structure that one fish cannot monopolise the entire aquarium. Do not multiply a litre figure mechanically; use the adults’ behaviour, tank dimensions and total bioload to size the system.

Provide stones, aquarium-safe wood, plants and established grazing surfaces without blocking the main swimming route. Use a secure lid because active cyprinids can jump, particularly when startled or newly introduced.

Water, flow and oxygen

Siamese Algae Eaters are associated with moving, oxygen-rich freshwater habitats. In the aquarium, use mature biological filtration, good surface movement and circulation that keeps oxygen available throughout the tank. Strong circulation is useful, but the layout should still include places where the fish can rest without fighting the full current constantly.

Current UK guidance uses roughly 22–27°C, pH 6.0–8.0 and moderate hardness as a practical starting range. Keep ammonia and nitrite at zero and monitor nitrate against your source water. Stable measured conditions are more important than sudden chemical adjustment to chase an exact number.

Do Siamese Algae Eaters really eat algae?

Yes, Crossocheilus are genuine grazers, but the evidence supports a more useful answer than “buy this fish and your algae disappears”. FishBase ecology and published stomach-content work support feeding on periphyton, diatoms and plant-associated material. Aquarium guidance also recognises Siamese Algae Eaters as active algae grazers.

What the evidence does not prove is a guaranteed black-beard-algae cure, a fixed clearance time or identical performance from every trade identity and individual fish. Algae growth should still trigger a review of lighting, organic waste, plant health, circulation and—where relevant—CO₂ stability.

Never reduce food to force a fish to graze more. A healthy animal is not an algae treatment product.

Feeding

Visible algae and biofilm can form part of the diet, but they are not a complete feeding plan. Offer an appropriate complete prepared food and suitable plant-based foods, with additional species-appropriate variety. Observe body condition and make sure all five fish actually reach food.

This matters especially as the fish grow. Juveniles may spend much of the day grazing, while older fish can become more interested in prepared food and general foraging. A spotless-looking aquarium can still contain an underfed algae eater.

Social behaviour

Current UK guidance commonly recommends either one Siamese Algae Eater or a group of five or more, rather than a casual pair or trio. This five-fish product therefore makes sense as a social group, but only where the aquarium is sized for the whole adult group.

Watch actual behaviour after introduction. Repeated chasing, one fish being excluded from food, weight loss or permanent hiding are signs that the group needs more space, more visual separation or intervention. A correct group count does not guarantee a peaceful hierarchy in every aquarium.

Tank mates

Choose active, peaceful community fish that share the same water conditions and are not so slow that they lose every feeding opportunity. Avoid highly territorial species that dominate the same lower and middle swimming zones, and be cautious with delicate long-finned fish in cramped setups.

Do not confuse Siamese Algae Eaters with Flying Foxes or Chinese Algae Eaters simply because the common names all mention algae. Those fish belong to different taxonomic groups or have different adult behaviour, and their care should be checked separately.

Why this listing does not promise black beard algae removal

“Siamese algae eater” has been promoted online as a guaranteed solution to black beard algae. That wording is too strong. The selected scientific evidence supports grazing behaviour and natural diets rich in periphyton/diatoms, but it does not establish a guaranteed home-aquarium cure or a result within a fixed number of days.

Before ordering

Choose this five-fish group only if you have a mature, well-oxygenated aquarium with substantial horizontal swimming room and capacity for five adults of roughly 14–16 cm. Reconsider if the plan is a small tank, a newly cycled aquarium or an attempt to solve an algae problem without addressing its underlying cause.