Harlequin rasbora care
Trigonostigma heteromorpha · Peninsular Malaysia, Sumatra and southern Thailand
Harlequin rasboras are copper fish with a black triangle and one of the easiest schooling fish for a planted community tank.
- Tank size
- 10 US gal or larger
- Temperature
- 72 to 81 °F (22 to 27 °C)
- Group size
- 8 or more
- Temperament
- Peaceful
- Adult size
- 2 in
- pH
- 6 to 7.5
- Hardness (GH)
- 2 to 12 dGH
- Lifespan
- 5 to 8 years
- Diet
- Omnivore
- Care level
- Easy
In a 10 gallon
20¼ × 10½ × 12 9/16 in outsideHow to keep harlequin rasboras
Harlequin rasboras are copper fish with a black triangle and one of the easiest schooling fish for a planted community tank. Keep eight or more in a 10 gallon or larger tank (a 20 gallon gives a group room to school) at 72 to 81 °F.
Diet: Omnivore: flakes, micro pellets, frozen daphnia. Fish food types compared · how often to feed.
Where they swim: Middle of the tank.
Harlequin rasbora tank mates
Share the temperature and water, and neither side eats, nips or bullies the other. Check the full group in the stocking checker.
Zebra danio
2 in · 10+ gal · 64–77 °F
Honey gourami
2 in · 10+ gal · 72–82 °F
Panda corydoras
2 in · 15+ gal · 68–77 °F
Otocinclus
2 in · 20+ gal · 72–79 °F
Forktail blue-eye rainbowfish
2 in · 10+ gal · 72–80 °F
Amano shrimp
2 in · 10+ gal · 68–80 °F
Ghost shrimp
2 in · 5+ gal · 65–80 °F
Mystery snail
2 in · 10+ gal · 68–82 °F
Keep apart
Pea puffer: Pea puffers belong in a tank of their own.
Red-tail dwarf puffer: Red-tail dwarf puffers belong in a tank of their own.
Everglades pygmy sunfish: Everglades pygmy sunfish belong in a tank of their own.
Axolotl: Axolotls belong in a tank of their own.
Electric blue crayfish: Electric blue crayfish belong in a tank of their own.
Discus: No shared temperature: harlequin rasboras need 72 to 81 °F, discus 82 to 88 °F.
What a harlequin rasbora tank needs
A tank of 10 US gallons or more (such as the 10 gallon) with a cover, and the equipment below.
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Aquarium Co-Op Easy Flow Sponge Filter, Small
A sponge filter gives gentle flow and cannot pull in small fish. It runs from an air pump, with airline tubing and a check valve, all sold separately.
hygger AquaFall Aquarium Filter, S
Rated by the maker for 7–10 US gal, which covers a 10 gallon harlequin rasbora tank without being built for a far bigger one.
Aqueon QuietFlow Internal Power Filter 5–15 gal
Rated by the maker for 5–15 US gal, which covers a 10 gallon harlequin rasbora tank without being built for a far bigger one.
hygger Precise Aquarium Heater 50W
Harlequin rasboras need 72 to 81 °F; most homes run cooler, so a heater holds the temperature.
API Freshwater Master Test Kit
Tests ammonia, nitrite, nitrate and pH, the readings that matter most before and after adding harlequin rasboras.
Seachem Prime 100 mL
Removes chlorine and chloramine from tap water at every water change.
Fluval Edge Thermometer
Shows the water temperature at a glance, so you know it stays within 72 to 81 °F.
More choices, each with the reason it is in or out: Filters for a 10 gallon tank · Heaters for a 10 gallon tank. We don’t list fish food: any good brand of the foods under Diet will do. Plan the whole tank's equipment →
Common harlequin rasbora problems
- Color fades in bare tanks and with constant chasing from bigger fish.
Test the water first whenever fish look unwell: see what your readings mean, then match the symptom. For disease, a vet who treats fish can diagnose it and advise treatment.
More to compare
Sources
Name, origin and adult size checked against Wikipedia: Trigonostigma heteromorpha. Temperature, pH, hardness, group size, lifespan and minimum tank size are common hobby guidance, not figures from that article. Ranges are the range the species tolerates; aim for the middle. Minimum tank sizes are for an adult group. Drawings are our own; photo credits follow.
Photo credits
Real photographs from Wikimedia Commons, resized and cropped to fit; each is used under the license named.
- Harlequin rasbora NasserHalaweh, CC BY-SA 4.0, via Wikimedia Commons
- Zebra danio Roundish, CC0, via Wikimedia Commons
- Honey gourami Antoon Dommerholt (Dutch Wikipedia), CC BY-SA 3.0, via Wikimedia Commons
- Panda corydoras Chronotopian, CC BY-SA 3.0, via Wikimedia Commons
- Otocinclus CHUCAO, CC BY-SA 3.0, via Wikimedia Commons
- Forktail blue-eye rainbowfish Dirk Godlinski, CC BY-SA 3.0, via Wikimedia Commons
- Amano shrimp Stefanie Leuker, CC0, via Wikimedia Commons
- Ghost shrimp Smithsonian Environmental Research Center, CC BY 2.0, via Wikimedia Commons
- Mystery snail Gabriel Resende Veiga, CC BY-SA 4.0, via Wikimedia Commons
- Pea puffer Beta Mahatvaraj, CC BY-SA 4.0, via Wikimedia Commons
- Red-tail dwarf puffer Neale Monks (English Wikipedia), CC BY-SA 3.0, via Wikimedia Commons
- Everglades pygmy sunfish Brian Gratwicke, CC BY 2.0, via Wikimedia Commons
- Axolotl LoKiLeCh, CC BY-SA 3.0, via Wikimedia Commons
- Electric blue crayfish Dirk Rohlfs, Public domain, via Wikimedia Commons
- Discus Patrick Farrelly, Public domain, via Wikimedia Commons
- Chili rasbora JoKrimmel, CC BY-SA 4.0, via Wikimedia Commons
- Celestial pearl danio Cisamarc, CC BY-SA 3.0, via Wikimedia Commons
- White cloud mountain minnow Petrtyl, CC BY 4.0, via Wikimedia Commons
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