Lambchop rasbora

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.

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.

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)

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

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

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)