Harlequin Rasbora
Trigonostigma heteromorpha
Also known as Harlequin, Red Rasbora
Edited by Ivan F. · Reviewed
Beginner verdict
A very peaceful, copper-colored schooling fish with a neat black wedge on its side, and one of the safest recommendations for newcomers. It places few demands on water chemistry, gets along with most small community fish, and shows its best color in a planted tank.
Care at a glance
- Min tank size
- 14 US gal
- Footprint
- 24 x 12 in
- Temperature
- 70–82 °F
- pH
- 5–7.5
- Hardness
- 1–12 dGH
- Swim zone
- Mid-Water
- Min group
- 8 fish
- Lifespan
- 5–8 years
Harlequin Rasbora care mistakes to avoid
The mistakes beginners most often make with this species.
- Do not buy just one or two. Keep at least 8 fish so they feel secure.
- Do not overstock a small tank. It is active and needs open swimming room.
- Skip large, boisterous companions, which will intimidate the school.
- Avoid a brightly lit, bare setup. Plants and shade bring out its copper color.
- Check your tank before you buy. Our sourced minimum is 14 US gallons.
Harlequin Rasbora tank mates and swim zone
Mid-Water
Spends most of its time in this part of the tank.
Poecilia reticulata
Xiphophorus maculatus
Xiphophorus hellerii
Betta splendens
Trichogaster chuna
Trichogaster lalius
Boraras brigittae
Chili Rasbora is small and shy, and is easily outcompeted for food by Harlequin Rasbora.
Tanichthys albonubes
Their temperature ranges barely overlap, so you will have little room for error.
Ancistrus cirrhosus
Bristlenose Pleco is much larger than Harlequin Rasbora and may frighten or even eat it.
Mikrogeophagus ramirezi
Their temperature ranges barely overlap, so you will have little room for error.
Pseudomugil furcatus
One needs much harder water than the other can tolerate.
Carassius auratus
Goldfish suit cooler water and are not suited to tropical tanks, so Harlequin Rasbora is a poor match.
Common tank-mate questions
Harlequin Rasbora feeding and care
How to feed
- Feed small flakes or micro pellets.
- Add live or frozen daphnia or baby brine shrimp, matching its natural micro-predator diet.
- Feed small portions you can see finished within a couple of minutes, because overfeeding fouls the water fast.
Telling males from females
Mature females are usually rounder in the belly and a little larger than the slimmer, more colorful males.
Plants that suit it
Species facts
- Family
- Cyprinidae
- Native to
- Malaysia, Singapore, Sumatra and Borneo
- Adult size
- 1.8 in (4.5 cm)
- Temperament
- Peaceful
- Social needs
- Schooling/Shoaling (6+)
- Diet
- Micro-Predator
- Water flow
- Gentle
- Substrate
- Any
- Live plants
- Yes - Loves Plants
- Shrimp
- Adult Shrimp Only
- Fin nipping
- None
- Vulnerable to nippers
- No
- Breeding
- Difficult in Home Tanks
Harlequin Rasbora FAQ
What size tank do Harlequin Rasboras need?
Our sourced minimum is 14 US gallons (54 liters), with a footprint of 60 x 30 cm. A bigger tank is always easier to keep stable.
How many Harlequin Rasboras should I keep?
Keep at least 8 fish. Bigger groups usually look better and behave more confidently.
What can live with Harlequin Rasboras?
Good matches on our list include Fancy Guppy, Platy and Swordtail. Avoid Endler's Livebearer and Molly.
How long do Harlequin Rasboras live?
Care guides report about 5–8 years. Stable water and a good diet make the biggest difference.
How is a harlequin different from a lambchop rasbora?
They look alike, but a harlequin is deeper-bodied with a broader black wedge, while a lambchop is slimmer with a narrower wedge.
Where to buy Harlequin Rasbora
We have not found a store that sells Harlequin Rasbora under its scientific name yet. We add stores as we confirm them.
Live animals and plants travel by courier. Check the store's live-arrival guarantee, and only buy once your tank has cycled (see how to cycle a fish tank).
Some US states restrict certain species. Check our US state aquarium rules table and your state's own rules before you buy.
Complete the tank
A forgiving setup with room for a small community.
Tank size for this species
At least 14 US gallons (54 L), 60 x 30 cm footprint
Filter
Hang-on-back or large sponge filter
Easy to maintain and strong enough for a community without blasting the fish.
We are still choosing products for this.
Heater
Adjustable heater, about 5 W per gallon: 100 W at 20 gallons, about 150 W at 29
Enough power to hold a stable temperature in most homes. Size up for a cold room.
We are still choosing products for this.
Water Conditioner
Dechlorinator such as Seachem Prime
Tap water contains chlorine or chloramine that harms fish.
Seachem Prime US
Fritz Complete Water Conditioner US
API Betta Water Conditioner US
sera aquatan Spain
Tetra AquaSafe Spain
Maker's page · Sold at Kiwoko · Sold at Tiendanimal · Sold at zooplus.es
Why we chose these (Best Water Conditioner for Betta Fish). Nobody here has used or tested them.
Test Kit
Liquid kit such as API Freshwater Master
Tracks ammonia, nitrite, nitrate and pH while the tank cycles.
API Freshwater Master Test Kit US
API General & Carbonate Hardness Test Kit US
Maker's page · Sold at The Shrimp Farm · Sold at Bulk Reef Supply
sera aqua-test box (Cl) Spain
JBL PROAQUATEST COMBISET Plus NH4 Spain
Why we chose these (Best Test Kit for a Freshwater Aquarium). Nobody here has used or tested them.
Cycle the tank before adding animals. See our guide on how to cycle a fish tank.