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 or more
- Lifespan
- 5–8 years
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.
Harlequin Rasbora care mistakes to avoid
- 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 setup
A forgiving setup with room for a small community.
TankAt least 14 US gal (54 L), 60 x 30 cm
The smallest tank our sources give for Harlequin Rasbora. We list only tanks that hold this volume (allowing 10%, so a standard size counts) and have at least this much floor.
Aqueon Standard Glass Aquarium 20 Long US
Aqueon Standard Glass Aquarium 29 Gallon US
Eheim clearTank 73 Spain
Why we chose these (Best 20-Gallon Fish Tank: 20 Long or 29?). Nobody here has used or tested them.
Starter kitA kit with the tank, filter and light in one box
We list only kits whose tank fits Harlequin Rasbora, up to twice its minimum volume. A kit whose heater has a fixed setting shows only when that setting is inside Harlequin Rasbora's temperature range.
Tetra Complete LED Aquarium Kit 20 Gallon US
Check the heater's setting
Tetra Starter Line LED Aquarium 54 L Spain
Heater preset to 25 °C
Tetra Starter Line LED Aquarium 80 L Spain
Heater preset to 25 °C
Why we chose these (Best Aquarium Starter Kit: What to Look For). Nobody here has used or tested them.
FilterHang-on-back or large sponge filter
Easy to maintain and strong enough for a community without blasting the fish.
Seachem Tidal 55 Power Filter US
Marineland Penguin PRO 175 Power Filter US
Eheim LiBERTY 130 Hang-on Filter Spain
Seachem Tidal 35 Power Filter Spain
Why we chose these (Best Filter for a 20 to 29-Gallon Tank). Nobody here has used or tested them.
HeaterKeep it at 70–82 °F (21–28 °C)
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.
Aqueon Pro Adjustable Heater 100 W US
Aqueon Submersible Glass Heater 100 W US
Eheim Thermocontrol e 100 Heater Spain
Tetra HT 100 Electronic Heater Spain
Why we chose these (Best Heater for a 20 to 29-Gallon Tank). Nobody here has used or tested them.
Water conditionerDechlorinator 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
Sold at Kiwoko · Sold at Tiendanimal · Sold at zooplus.es · Maker's details
Why we chose these (Best Water Conditioner for Betta Fish). Nobody here has used or tested them.
Test kitLiquid 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
See it at The Shrimp Farm (a retailer; affiliate link) · Sold at Bulk Reef Supply · Maker's details
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.
SubstrateDecor is not critical; a dark substrate shows its colour best.
We are still choosing products for this.
Hiding places and decorWood roots and branches that make shady spots, dried leaves and floating plants suit it.
We are still choosing products for this.
PlantsSafe with live plants
Cycle the tank before adding animals. See our guide on how to cycle a fish tank.
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.
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.
Harlequin Rasbora facts and sources
- 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
Sources
- Seriously Fish: Tank size, water ranges and behavior
- FishBase: Cross-check of water ranges and size
Lifespans are approximate and come from aquarium care guides, because these databases rarely publish them.
Where sources differ, we show the Seriously Fish aquarium figures.
Spotted something wrong? Report a parameter correction. For a sick fish, see our veterinary disclaimer.