What's the difference between a real SAE and a false SAE?

The real Crossocheilus oblongus has a black stripe that runs from nose to tail AND extends into the tail fin. False SAEs — flying foxes (Epalzeorhynchus kalopterus) and red-tail sharks — have a stripe that stops at the tail base OR a different-coloured tail [2]. The real SAE also has a completely flat ventral profile and almost no colour on the fins. If the fins have red, yellow, or black markings — it's not the real SAE.

Do Siamese algae eaters actually eat black beard algae?

Yes, and they're the only fish in the UK trade that does [4]. Plecos, otocinclus, flying foxes, and shrimp all refuse BBA. The real SAE will graze BBA down over 2–4 weeks depending on infestation density. Bristlenose plecos won't touch it. Shrimp won't touch it. This is the one job SAEs are genuinely unique at.

Can I keep one Siamese algae eater or do I need a group?

Keep either ONE alone, OR a group of FIVE OR MORE. Never 2–4. In groups of 2–4 the strongest fish bullies the rest into hiding and they starve [2]. Solo keeping works fine — they're not obligate schooling fish. If you want multiples, 5+ disperses the territorial aggression enough that no one fish gets singled out.

How big do Siamese algae eaters get?

14–16 cm as adults, which is why we list the minimum tank at 120 L [1]. Juveniles in the shop are 3–5 cm and it's tempting to keep them in a 60 L — that works for 6–12 months, but they grow fast. Plan for their adult size before you buy.

Are Siamese algae eaters aggressive?

Peaceful as juveniles, semi-territorial as adults. A single adult in a planted 120 L is genuinely peaceful with everything. Two adults in anything under 200 L means one dominates. Toward other species — they're fine with tetras, rasboras, most peaceful community fish. They can get nippy toward slow-moving or long-finned fish (angelfish, guppies) if underfed.

Do Siamese algae eaters need live plants?

Yes — they're happiest in a planted tank with plenty of surfaces to graze. They're not destructive to plants (unlike some other algae eaters that will shred soft plants), but they need the grazing surface a planted tank provides [5]. A bare tank with just rocks or driftwood leaves them bored and they start chasing tank mates.

What do Siamese algae eaters eat besides algae?

Omnivore. They eat algae, biofilm, leftover fish food, sinking pellets, frozen bloodworms, blanched courgette, and even small insect larvae. Don't rely on algae alone — once the tank is mature and algae is under control, you need to supplement with sinking pellets 2–3 times a week.

Can SAEs live with shrimp?

Adult shrimp yes, shrimp fry will be eaten. In a mature planted tank with dense moss cover, a neocaridina colony co-exists with one SAE indefinitely — the SAE keeps the fry count in check but doesn't wipe out adults.

Why is my Siamese algae eater not eating algae?

Three common reasons: (1) fed too much other food — cut back on pellets and they'll graze again; (2) wrong species — check it's actually a real SAE and not a flying fox (which eats pellets but ignores BBA); (3) stressed in a new tank — give it 3–4 weeks to settle. A healthy SAE in a mature tank will graze visibly for 2–4 hours a day.

How long do Siamese algae eaters live?

5–10 years in a well-maintained planted tank [1]. That's a commitment comparable to a small dog. Worth thinking about before you buy — an impulse-buy SAE is a 7-year commitment at minimum.

Siamese Algae Eater UK Buying Guide (2026)

Why this page exists — and why every other SAE guide gets the basics wrong

Most "Siamese algae eater" Google results are written by people who have never identified the species in person. They confuse four similar-looking fish, recommend groups that don't work, and skip the single crucial fact about the species: it's the only fish that eats black beard algae.

I'm James. I've run planted tanks with SAEs through two BBA outbreaks and one hair-algae surge. This is the version of the guide I'd send to a friend who just bought a CO₂ rig and is seeing the first black tufts on their driftwood.

A Silver Flying Fox — the most commonly mis-sold false SAE, for side-by-side comparison

A Silver Flying Fox (Epalzeorhynchos kalopterus). Note the yellow and black fin markings — the immediate tell that separates this from the real Siamese algae eater, whose fins are clear. Photo: Tropical Fish Co warehouse.

Five facts most "SAE buying guides" miss

"Siamese algae eater" used to mean four different species. The taxonomic revision in 2019 split what was historically sold as a single species into multiple distinct species — Crossocheilus oblongus, C. siamensis, C. atrilimes, and several others ^[?]. Most UK stock is now confirmed C. oblongus.
SAEs are the only fish that eats black beard algae. Not exaggeration — it's genuinely the only species in the UK freshwater trade that grazes BBA. This is the main reason planted aquascapers keep them ^[?].
Real SAEs have NO colour on their fins. Their fins are clear or very pale grey. If you see red, yellow, orange, or strong black markings on the dorsal, tail, or pectoral fins — it's a false SAE ^[?].
They can live 10 years. Well-kept adults in a stable planted tank routinely reach 10 years old ^[?].
They tolerate the full UK tap-water range. Hardness from 5 to 20 dGH and pH from 6.5 to 8.0 ^[?], which means every UK postcode's tap water works ^[?].

How to tell a real Siamese algae eater from a fake one

This is the single most important section of the page.

Head-to-head: the four fish sold as "Siamese algae eater" in UK shops

Species	Tail stripe?	Fin markings?	Eats BBA?	Adult size	UK price
Real SAE (Crossocheilus oblongus)	✓ Extends through tail	None (clear fins)	✓ Yes	14–16 cm	£25–£35
Flying Fox (Epalzeorhynchus kalopterus)	✗ Stops at tail base	Yellow/red on dorsal + tail	✗ No	14 cm	£5–£8
False Siamensis (C. langei)	Extends partway into tail	Some black on dorsal	Partial	12 cm	£10–£15
Red-tail Shark (Epalzeorhynchos frenatum)	✗ Solid black body, red tail	Solid red tail	✗ No	15 cm	£4–£8

The single diagnostic is the tail stripe + fin colouration. If the stripe stops at the tail base, it's not the real SAE. If the fins have colour markings, it's not the real SAE.

The black beard algae problem — why you bought this guide

A Snow White Bristlenose Pleco grazing on driftwood — the SAE's natural partner for general-algae control

A Snow White Bristlenose Pleco. Plecos and SAEs work in tandem — plecos handle green algae and biofilm, SAEs handle BBA ^[?]. Neither species alone controls everything in a planted tank. Photo: Tropical Fish Co warehouse.

What BBA actually is

Black beard algae is a red algae (Audouinella / Compsopogon complex) that appears as dark tufts on driftwood, plant leaves, and filter outlets. It loves moving water and thrives in tanks where CO₂ is unstable or where flow patterns create dead spots.

The biological control options (ranked)

Real Siamese algae eater — the only species that actually eats it. Expect 2–4 weeks to clear a visible outbreak.
Amano shrimp — will nibble BBA when very hungry; not reliable, but they chew down the early-stage tufts.
Everything else on the internet — myth. Bristlenose plecos, otocinclus, ramshorn snails, flying foxes, cherry shrimp: all ignore BBA ^[?].

Chemical control alternative

Excel / liquid carbon (Seachem Flourish Excel, APT Fix) kills BBA on contact when spot-treated with a syringe. Works but kills mosses and vallisneria if overdone. Most aquascapers combine: an SAE for ongoing control + Excel spot-treatment for stubborn patches.

Tank size and stocking

Minimum tank: 120 L for a single SAE. Recommended: 200 L+ for a pair or group.

Stocking guide by tank size:

120 L planted — 1 SAE + full community below (tetras, shrimp, corydoras, otocinclus) — the classic single-SAE planted setup
180 L planted — 1 SAE + 2 L-number plecos OR a pair of dwarf cichlids — still solo for the SAE, larger community around it
250 L+ planted — 5 SAEs + any compatible community — the first tank size where keeping them in a group works

Watch: a mature planted tank with an SAE grazing

120 L mature Dutch-style planted tank. The SAE grazes on the driftwood's BBA-prone zones daily for 2–3 hours. Photo: James Okafor editorial.

Tank mates for a Siamese algae eater

SAEs work well with almost anything peaceful. The rules are:

No fin-nippers — barbs will nip the SAE's dorsal
No territorial species — red-tail sharks, blue rams, and adult bettas will fight a settled SAE
Nothing small enough to eat — fry from livebearers will be picked off

Safe community pairings:

Schooling tetras — cardinals, embers, harlequin rasboras, neons all work well. The SAE ignores water-column fish.
Corydoras catfish — different feeding zone (substrate), no conflict.
Otocinclus — different algae preference, different feeding zone. Excellent partnership.
Amano shrimp — safe in large enough tanks. Juvenile shrimp may be snacked on.
Bristlenose pleco — compatible if the tank is 180 L+. Below that, territorial overlap becomes an issue.

When your SAE arrives — our UK delivery protocol

SAEs ship well. Their body size and low stress response mean they tolerate the 14–20 hour overnight courier journey better than smaller, more delicate tetras.

Open in a quiet room, lights dim.
Float the bag 20 minutes sealed.
Drip-acclimate 40 minutes at 1–2 drops per second.
Net into the tank.
Lights off 2 hours — SAEs need to find their preferred hiding spot before lights come on.
No feeding for 24 hours. They'll start grazing on whatever algae is in the tank within 48 hours.

Don't buy 3 SAEs thinking they'll school

The single most common mistake I see: new planted-tank keepers buy 3 SAEs because "they shoal". They don't. In a group of 3 one dominates and the other two hide behind the heater and starve. Either buy ONE for any tank under 250 L, or buy FIVE+ for a tank 250 L+ ^[?].

Ready for more?

Looking at the other algae specialists? See our ancistrus pleco guide for the best biological control on green algae, or the otocinclus care guide for the nano-tank glass-cleaner. The amano shrimp care guide covers the invertebrate half of the algae crew.

Shopping for the full planted-tank algae stack? Start at the catfish & plecos hub.

Siamese Algae Eater UK: The Complete 2026 Planted-Tank Guide