Lambchop rasbora
Trigonostigma espei
Also known as: Espei rasbora, Espe's rasbora, False harlequin rasbora
This is that tiny coppery-orange rasbora with the sharp "lambchop" black wedge on its side-super slick-looking in a planted tank. Keep a proper little gang of them and they'll cruise the midwater together, flashing color way more than when they're kept in a sad little trio. They're gentle, easy to feed, and honestly one of my favorite small-school fish for calmer community setups.
The Lambchop rasbora exhibits a striking orange body with a distinctive black stripe running horizontally from the snout to the caudal fin.
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Quick Facts
Size
2.5 cm SL (~1 inch)
Temperament
Peaceful
Difficulty
Beginner
Min Tank Size
15 gallons
Lifespan
4-6 years
Origin
Southeast Asia (Thailand, Cambodia; also reported from Phú Quốc, Vietnam)
Diet
Omnivore - fine flakes/micro pellets plus frozen/live foods (daphnia, brine shrimp, small insect larvae)
Water Parameters
23-28°C
6-7.5
2-12 dGH
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Calculate heater sizeCare Notes
- Keep them in a real group (8-12+); with only a couple they get shy and hide, and the colors stay washed out.
- A 10-20 gallon with plants and some cover is perfect-think dimmer light, dark substrate, and a few open lanes for them to school through.
- They're happiest in soft-ish, slightly acidic water: aim around 74-80°F (23-27°C), pH ~6.0-7.2, and keep nitrates low with regular water changes.
- Feed small stuff they can actually fit in their mouths-micro pellets, crushed flakes, and frozen baby brine shrimp/daphnia; tiny meals 1-2x a day beats dumping food in.
- Great with other peaceful nano fish (ember tetras, other rasboras, small gouramis) and shrimp; skip fin-nippers and anything big enough to see them as snacks.
- If they start clamping fins or fading out, check for stress from bright light/no cover or being under-stocked-these guys color up when they feel safe.
- Breeding is doable: a dense clump of fine plants or a spawning mop, slightly softer water, and well-fed adults can give you eggs-pull the parents after spawning because they'll snack on them.
Compatibility
Good Tankmates
- Other small, chill schooling fish (harlequin rasboras, ember tetras, neon/cardinal tetras) - they match the same "hang in the middle and vibe" energy and nobody gets picked on.
- Corydoras (pygmy, panda, pepper, etc.) - they stick to the bottom, super peaceful, and lambchops don't care about them at all. Nice active combo.
- Kuhli loaches - nocturnal noodles that keep to themselves. Great if you've got plants/wood and soft-ish water; zero drama with espei.
- Small, calm gouramis (honey gourami, sparkling gourami) - usually works great as a gentle "centerpiece," just don't cram the tank and give them cover.
- Dwarf shrimp + snails (amano, cherries if there's cover; nerites/mystery snails) - lambchops mostly ignore adults. Baby shrimp might get snacked if the tank's bare, so plants/moss help.
- Otocinclus - peaceful algae crew that won't compete or bully. They do best once the tank's mature and stable, but they're a really nice match.
Avoid
- Nippy fin-biters (serpae tetras, tiger barbs, some "spicy" danios) - lambchops are peaceful and get stressed when stuff starts chasing and shredding fins.
- Bigger mouthy fish that see small rasboras as snacks (most medium/large cichlids, big gouramis, some larger barbs) - if it can fit an espei in its mouth, it'll eventually try.
- Super aggressive territory guards (bettas that hate company, especially in smaller tanks) - sometimes it works, but it's a coin flip and the rasboras usually pay the price when it doesn't.
- Slow fancy-finned fish that can't get away (long-fin bettas, fancy guppies) - either the fancy fish gets harassed by other tankmates, or the rasboras get outcompeted/stressed; it's just not the smoothest mix.
1) Where they come from
Lambchop rasboras (Trigonostigma espei) come from Southeast Asia—think slow, warm forest streams and swampy areas in Thailand and Cambodia. The water’s often tea-colored from leaf litter, with gentle flow and lots of plants along the edges.
If you’ve ever kept harlequin rasboras, these feel like their slightly smaller, punchier-colored cousins.
2) Setting up their tank
These are super beginner-friendly, but they look and act their best in a calm, planted setup. Give them some cover and they’ll be out and about instead of hugging the corners.
- Tank size: 10 gallons works for a group, 20 long is even nicer for a bigger school
- Group size: aim for 8–12+ (they relax and color up in numbers)
- Temp: ~24–28°C / 75–82°F
- pH/hardness: they’re flexible, but slightly acidic to neutral and softer water keeps them looking great (roughly pH 6.0–7.5)
- Flow: gentle—think “lazy stream,” not river rapids
- Lighting: moderate; too bright without cover can make them skittish
Plants help a ton. I’ve had the best results with lots of stem plants (like rotala or hygrophila), some floating plants to dim the light, and a bit of open swimming space up front.
Toss in a handful of botanicals (catappa leaf, alder cones, or just a few clean dried leaves) if you like the blackwater look. It also seems to settle them down and brings out that copper-orange body.
They don’t love “new tank chaos.” Wait until the tank is cycled and stable—ammonia and nitrite spikes hit small rasboras fast.
3) What to feed them
They’re easy eaters. In my tanks they go nuts for small foods, and a varied menu keeps their color strong and their bellies nicely rounded (without looking stuffed).
- Daily staples: quality micro pellets, small flakes crushed between your fingers
- Frozen: baby brine shrimp, daphnia, cyclops (great for conditioning)
- Live (if you’ve got it): baby brine shrimp, microworms, grindal worms
- Occasional treat: bloodworms (go easy—easy to overdo)
Feed small amounts 1–2 times a day. If food is hitting the substrate untouched, you’re feeding too much or the pieces are too big.
4) Behavior and tankmates
Lambchops are peaceful, school tightly, and do that fun “flash and shuffle” movement when they feel safe. Males will spar a bit—more like showing off than fighting.
They’re also a nice confidence fish. In a community tank, they often help shyer fish come out once the rasboras start cruising around.
- Great tankmates: other small rasboras, ember tetras, small tetras, peaceful danios (not the hyper ones), kuhli loaches, otocinclus, small corydoras, shrimp (adult shrimp usually fine)
- Also works: honey gourami, sparkling gourami, calm bettas (depends on the betta’s attitude)
- Skip: aggressive fish, fin nippers, big gouramis/cichlids, and anything that sees a 1-inch fish as a snack
If they’re hiding all the time, it’s usually one of three things: the group is too small, the tank is too bare/bright, or there’s a bully in the neighborhood.
5) Breeding tips (if you want to try it)
They’re egg scatterers and tend to spawn in plants. You can get lucky in a mature planted tank, but if you want fry, you’ll need to play defense—adults will eat eggs and tiny fry.
- Set up a small breeding tank (5–10 gal) with a sponge filter
- Use fine-leaf plants (java moss) or spawning mops; they like to place eggs under leaves
- Slightly warmer, softer water helps (around 26–28°C / 79–82°F, and not too hard)
- Condition with live/frozen foods for a week or two
- Move the adults out after you spot spawning (or after a day), or use a mesh/egg grate so eggs drop out of reach
The tiniest hurdle is first food. Have infusoria or a powdered fry food ready, then move to baby brine shrimp once they can take it.
6) Common problems to watch for
Most issues with lambchops trace back to stress from the environment. They’re small fish, so little problems become big problems quickly.
- Faded color / clamped fins: usually stress (bright tank, not enough cover, poor water, too-small group)
- Ich/white spot after new additions: quarantine new fish if you can; these guys can pick up parasites when stressed
- Sudden losses in a new setup: almost always cycling/ammonia issues or big temperature swings
- Not eating: check for bullying, oversized food, or a fish that arrived already thin (internal parasites happen)
Keep your maintenance steady: regular water changes, don’t let nitrates creep up, and avoid big swings. They handle “average” water fine—what they hate is instability.
A tight-fitting lid is worth it. They’re not notorious jumpers, but a startled school can launch, especially during lights-on/lights-off moments.
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