Siamese Algae Eater Care Guide: The BBA Destroyer

The Siamese algae eater (Crossocheilus oblongus) holds a unique position in the freshwater hobby: it is one of the very few fish that reliably eats black beard algae (BBA), the bane of planted tank enthusiasts worldwide. This has made it one of the most sought-after utility fish in aquascaping, and for good reason.

However, the Siamese algae eater is also one of the most misidentified fish in the trade. Lookalike species are frequently sold under the same name, and what starts as a small, diligent algae-eating juvenile can grow into a sizeable, somewhat lazy adult. Understanding these realities is key to making the most of this fish in your Singapore aquarium.

True SAE vs Impostors

This is the most important section in this guide. Three fish are commonly confused in the aquarium trade, and only one is the true Siamese algae eater that effectively controls BBA. Learning to tell them apart before you buy saves frustration and money.

True Siamese Algae Eater (Crossocheilus oblongus)

• Bold, black horizontal stripe running from the snout to the tip of the tail fin (the stripe extends into the caudal fin — this is the key identifier)
• The stripe has ragged, uneven edges, not perfectly straight
• No coloured or dark stripes above the black stripe — the area above is a clean olive or golden-brown
• Single pair of small, forward-pointing barbels on the upper lip
• Rests on the substrate by supporting itself on its pectoral and pelvic fins, with the body angled slightly upward
• Maximum size: 14-16 cm

False Siamese Algae Eater / Flying Fox (Epalzeorhynchos kalopterus)

• Black stripe also runs from snout to tail, but it does NOT extend into the caudal fin — it stops at the tail base
• The stripe has smoother, cleaner edges
• A noticeable gold or yellow stripe runs above the black stripe
• Two pairs of barbels (more prominent than the true SAE’s)
• More territorial and aggressive than true SAEs
• Does NOT eat black beard algae

Siamese Flying Fox (Crossocheilus atrilimes)

• Very similar to the true SAE and sometimes sold as one
• The black stripe has a bright, well-defined golden edge above it
• Flap at the corner of the mouth is more prominent
• Less effective at eating BBA than the true SAE

When purchasing from shops in Singapore, examine the fish carefully before buying. Ask the shopkeeper if they can confirm the species. At Gensou, we take care to stock correctly identified true SAEs — misidentification is a widespread issue in the aquarium trade that causes genuine disappointment when the fish does not perform as expected.

Black Beard Algae Eating

The true SAE’s claim to fame is its appetite for black beard algae (Audouinella / Rhodochorton), a stubborn red algae that forms dark tufts on equipment, hardscape and slow-growing plant leaves. BBA is the algae that most other fish — including bristlenose plecos, otocinclus and Amano shrimp — will not touch.

Young SAEs are the most effective BBA grazers. They methodically work through tufts of BBA, pulling and nibbling until the surface is clean. In a planted tank with a moderate BBA problem, two or three juvenile SAEs can make a noticeable difference within a few weeks.

However, it is important to set realistic expectations:

• SAEs reduce BBA but may not eliminate a severe outbreak on their own — you still need to address the root cause (usually fluctuating CO2 levels or poor water circulation)
• SAEs also eat other types of algae, including hair algae, green algae and some film algae
• Effectiveness diminishes significantly as the fish matures (more on this below)
• If well-fed with commercial foods, SAEs may ignore algae altogether

Size and Growth

This is where many aquarists are caught off-guard. Siamese algae eaters sold in shops are typically 3-5 cm — small, slim and unassuming. They grow to 14-16 cm, making them a medium-sized fish that requires significantly more space than most people anticipate when buying that cute little algae eater.

Growth is relatively fast in well-fed aquariums. Expect a juvenile to reach 8-10 cm within the first year and full size within 18-24 months. They are also moderately long-lived, with a lifespan of 8-10 years in good conditions.

Tank Size and Setup

Given their adult size and active swimming behaviour, SAEs need more space than casual buyers realise.

• Minimum: 100 litres (75 cm long) for a single SAE or a pair
• Recommended: 150-200 litres for a small group of three to four
• Planted tanks: SAEs thrive in heavily planted aquascapes with good flow

Provide a well-planted environment with driftwood, rocks and open swimming lanes. SAEs appreciate moderate to strong water flow, reflecting their natural riverine habitat. A canister filter with a spray bar or lily pipe provides ideal conditions.

If you are setting up a planted tank and want help integrating SAEs into the design, our custom aquarium service can advise on species selection and aquascape layout.

Water Parameters

SAEs prefer slightly cooler water than Singapore naturally provides. In non-air-conditioned rooms, a cooling fan is advisable, particularly during the hotter months from March to June. Good surface agitation also increases dissolved oxygen, which active fish like SAEs need.

Remember to treat PUB tap water with a conditioner that handles chloramine — standard dechlorinators designed for chlorine alone may not fully neutralise Singapore’s water treatment chemicals.

Feeding

SAEs are omnivores that will eat almost anything offered. This versatility is part of the problem — if given tasty commercial foods regularly, they quickly lose interest in algae.

Feeding Strategy for Maximum Algae Eating

• Limit commercial food: If your primary goal is algae control, feed sparingly. Offer sinking pellets or wafers only two to three times per week
• Blanched vegetables: Zucchini, cucumber and spinach supplement their diet without eliminating algae appetite
• Protein: Occasional frozen bloodworms or brine shrimp are appreciated but should not be a daily offering
• Let them graze: A hungry SAE is a working SAE. Do not overfeed community tank mates either, as SAEs will scavenge leftovers

Behaviour as They Mature

This is perhaps the most important practical consideration for anyone buying a Siamese algae eater specifically for algae control. SAE behaviour changes significantly as they grow.

Juvenile SAEs (3-8 cm)

• Active, enthusiastic algae grazers
• Schooling behaviour — prefer groups of three or more
• Peaceful and shy
• Constantly moving, picking at surfaces

Adult SAEs (10-16 cm)

• Substantially reduced algae eating — many adults stop eating BBA entirely
• More interested in commercial foods, vegetables and even tender plant leaves
• Can become somewhat territorial, chasing tank mates from favourite resting spots
• Less active overall, spending more time resting on the substrate or perched on hardscape
• May nip at slow-moving fish or long-finned species

This behavioural shift does not make adult SAEs bad fish — they remain attractive, interesting and generally peaceful community members. But if you bought them solely for BBA control, you may be disappointed as they mature. Plan accordingly: enjoy them as part of your community rather than relying on them as a permanent algae solution.

Tank Mates

Juvenile SAEs are excellent community fish. Adults are still largely peaceful but can be boisterous. Compatible tank mates include:

• Medium-sized tetras (rummy-nose, Congo, emperor) — fast enough to avoid any chasing
• Rasboras — harlequin and other robust species
• Corydoras catfish — different feeding niche, no conflict
• Barbs (cherry, gold, tiger) — active fish that match SAE energy
• Gouramis — larger species like pearl gouramis coexist well
• Bristlenose plecos — occupy different algae niches without competition

Avoid housing adult SAEs with very small fish (neon tetras in small tanks), long-finned bettas, or slow-moving fancy guppies, as mature SAEs may pester or nip at them. Also avoid other bottom-dwelling territorial fish like red-tailed black sharks.

Jumping Tendency

Like many riverine cyprinids, SAEs are capable jumpers. They are particularly prone to leaping when:

• Startled by sudden movements, loud noises, or lights switching on abruptly
• Stressed by poor water quality or aggressive tank mates
• Recently introduced to a new tank (the first 48 hours are highest risk)

A tight-fitting lid or cover glass is essential. If you prefer an open-top aquascape, lower the water level by at least 8-10 cm and consider floating plants at the surface, which can deter jumping. In Singapore’s humid climate, a glass lid also reduces evaporation.

Frequently Asked Questions

How many Siamese algae eaters should I keep?

SAEs are social fish that do best in groups of three or more when young. As they mature, they become more independent and can be kept singly if tank space is limited. For algae control in a planted tank, two to three juveniles in a 150-litre tank is a good starting point. Just remember they will all grow to 14-16 cm.

Will a Siamese algae eater eat all my black beard algae?

Young SAEs will significantly reduce BBA, but they rarely eliminate a severe outbreak completely. More importantly, BBA returns if the underlying cause is not addressed. BBA typically thrives when CO2 levels fluctuate or water circulation is poor. Use SAEs as part of a broader strategy that includes stable CO2, good flow and proper lighting management.

My SAE has stopped eating algae. What happened?

This is normal adult behaviour. As SAEs mature, they lose interest in algae, especially if well-fed with commercial foods. To encourage algae eating, reduce the amount and frequency of supplemental feeding. However, some mature SAEs simply stop eating algae regardless — this is a well-documented aspect of the species. Consider adding younger SAEs or supplementing with Amano shrimp for ongoing algae control.

Can I keep a Siamese algae eater in a nano tank?

No. Despite being sold as small juveniles, SAEs are active fish that grow to 14-16 cm. They are unsuitable for tanks under 100 litres. For nano tanks needing algae control, consider otocinclus catfish, Amano shrimp or nerite snails instead.

The Siamese algae eater remains one of the most useful fish in the planted aquarium hobby, provided you understand its strengths and limitations. For help with algae management, species selection or planted tank design, visit Gensou at 5 Everton Park or get in touch through our contact page. Our team can help you build a balanced aquascape that stays algae-free long-term.

Related Reading

• Otocinclus vs Siamese Algae Eater: Which Algae Eater Is Right?
• Siamese Algae Eater vs Chinese Algae Eater: Key Differences
• Siamese Algae Eater vs Flying Fox: Identification and Behaviour
• Amano Shrimp vs Otocinclus: Which Algae Crew Wins?
• Blue Acara Cichlid Care Guide: The Overlooked Gem