Aquariumrasbora & danio · freshwater
Harlequin Rasbora: adult size, tank size & tankmates
The Harlequin Rasbora (Trigonostigma heteromorpha) grows to about 2.1 in (4.5 cm SL). It needs a tank at least 24 inches long and about 14 gallons. Keep at least 8 together, at 70–82°F.
How big it really gets
Drawn to scale against common tank lengths. Green bars meet the minimum tank length from our sources.
Will it fit your tank?
Quick facts
- Adult size
- 2.1 in (4.5 cm SL)
- Minimum tank
- 24 inches long and about 14 gallons
- Temperature
- 70–82°F
- pH
- 5–7.5
- Hardness
- 1–12 dGH
- Group size
- 8+
- With other fish
- peaceful
- With its own kind
- peaceful
- Swims
- middle of the tank
- Diet
- carnivore
- Care level
- beginner
- Lifespan
- not stated in sources
Watch for: may eat baby shrimp
Harlequin Rasbora tankmates
Checked with the same rules as our tank builder: temperature overlap, pH and hardness, predation and mouth size, fin-nipping and temperament. Tank size is left out here; check it in the builder.
Good tankmates
- Neon TetraAdult ~1.4 in · 70–77°F
- Cardinal TetraAdult ~1.7 in · 73–84°F
- Ember TetraAdult ~0.9 in · 68–82°F
- Chili RasboraAdult ~0.9 in · 68–82°F
- Celestial Pearl DanioAdult ~1 in · 68–79°F
- Cherry BarbAdult ~2.4 in · 68–81°F
- Rummy-nose TetraAdult ~2.4 in · 73–79°F
- Black Neon TetraAdult ~1.7 in · 73–82°F
- Glowlight TetraAdult ~1.9 in · 75–82°F
- Lemon TetraAdult ~1.9 in · 68–82°F
Use caution
- Endler's LivebearerNeeds careHarlequin Rasbora (1–12 dGH) and Endler's Livebearer (15–35 dGH) prefer different water hardness.
- Dwarf GouramiNeeds careDwarf Gourami can bully smaller, peaceful Harlequin Rasbora.
- BettaNeeds careBetta can bully smaller, peaceful Harlequin Rasbora.
- German Blue RamNeeds careHarlequin Rasbora and German Blue Ram only share 81–82°F. That's a tight window.
- AngelfishNeeds careAngelfish can bully smaller, peaceful Harlequin Rasbora.
- Cherry ShrimpHarlequin Rasbora may eat baby Cherry Shrimp. Adults are usually safe, but expect fewer shrimplets.
- Amano ShrimpHarlequin Rasbora may eat baby Amano Shrimp. Adults are usually safe, but expect fewer shrimplets.
- Nerite SnailHarlequin Rasbora (pH 5–7.5) and Nerite Snail (pH 8–8.4) prefer different pH.
Avoid
- Chinese Algae EaterOutgrows tanksChinese Algae Eater grows 6× longer than Harlequin Rasbora and may treat it as food.
- Convict CichlidNeeds careConvict Cichlid is aggressive toward tankmates. Harlequin Rasbora is peaceful.
- Iridescent SharkOutgrows tanksIridescent Shark eats small fish, and Harlequin Rasbora only grows to about 2.1 in.
- OscarOutgrows tanksOscar eats small fish, and Harlequin Rasbora only grows to about 2.1 in.
All 105 species we checked against the Harlequin Rasbora
| Species | Verdict | Why |
|---|---|---|
| African Dwarf Frog | Compatible | No conflicts found |
| Assassin Snail | Compatible | No conflicts found |
| Bala Shark | Compatible | No conflicts found |
| Black Neon Tetra | Compatible | No conflicts found |
| Bleeding Heart Tetra | Compatible | No conflicts found |
| Bolivian Ram | Compatible | No conflicts found |
| Bristlenose Pleco | Compatible | No conflicts found |
| Bronze Cory | Compatible | No conflicts found |
| Buenos Aires Tetra | Compatible | No conflicts found |
| Bumblebee Goby | Compatible | No conflicts found |
| Cardinal Tetra | Compatible | No conflicts found |
| Celestial Pearl Danio | Compatible | No conflicts found |
| Cherry Barb | Compatible | No conflicts found |
| Chili Rasbora | Compatible | No conflicts found |
| Clown Killifish | Compatible | No conflicts found |
| Clown Loach | Compatible | No conflicts found |
| Clown Pleco | Compatible | No conflicts found |
| Cockatoo Dwarf Cichlid | Compatible | No conflicts found |
| Common / Comet Goldfish | Compatible | No conflicts found |
| Common Pleco | Compatible | No conflicts found |
| Congo Tetra | Compatible | No conflicts found |
| Denison Barb | Compatible | No conflicts found |
| Diamond Tetra | Compatible | No conflicts found |
| Discus | Compatible | No conflicts found |
| Dwarf Neon Rainbowfish | Compatible | No conflicts found |
| Ember Tetra | Compatible | No conflicts found |
| Giant Danio | Compatible | No conflicts found |
| Glass Catfish | Compatible | No conflicts found |
| Glowlight Tetra | Compatible | No conflicts found |
| Gold Barb | Compatible | No conflicts found |
| Guppy | Compatible | No conflicts found |
| Head-and-tail-light Tetra | Compatible | No conflicts found |
| Hillstream Loach | Compatible | No conflicts found |
| Honey Gourami | Compatible | No conflicts found |
| Japanese Trapdoor Snail | Compatible | No conflicts found |
| Julii Cory | Compatible | No conflicts found |
| Kribensis | Compatible | No conflicts found |
| Kuhli Loach | Compatible | No conflicts found |
| Lambchop Rasbora | Compatible | No conflicts found |
| Lemon Tetra | Compatible | No conflicts found |
| Malaysian Trumpet Snail | Compatible | No conflicts found |
| Marbled Hatchetfish | Compatible | No conflicts found |
| Moonlight Gourami | Compatible | No conflicts found |
| Neon Tetra | Compatible | No conflicts found |
| Odessa Barb | Compatible | No conflicts found |
| Otocinclus | Compatible | No conflicts found |
| Panda Cory | Compatible | No conflicts found |
| Pea Puffer | Compatible | No conflicts found |
| Pearl Danio | Compatible | No conflicts found |
| Pearl Gourami | Compatible | No conflicts found |
| Penguin Tetra | Compatible | No conflicts found |
| Peppered Cory | Compatible | No conflicts found |
| Platy | Compatible | No conflicts found |
| Pristella Tetra | Compatible | No conflicts found |
| Pygmy Cory | Compatible | No conflicts found |
| Ramshorn Snail | Compatible | No conflicts found |
| Rosy Barb | Compatible | No conflicts found |
| Rummy-nose Tetra | Compatible | No conflicts found |
| Scissortail Rasbora | Compatible | No conflicts found |
| Serpae Tetra | Compatible | No conflicts found |
| Siamese Algae Eater | Compatible | No conflicts found |
| Silver Hatchetfish | Compatible | No conflicts found |
| Silver Tip Tetra | Compatible | No conflicts found |
| Sparkling Gourami | Compatible | No conflicts found |
| Sterbai Cory | Compatible | No conflicts found |
| Swordtail | Compatible | No conflicts found |
| Tiger Barb | Compatible | No conflicts found |
| Tinfoil Barb | Compatible | No conflicts found |
| Upside-down Catfish | Compatible | No conflicts found |
| Weather Loach | Compatible | No conflicts found |
| White Cloud Mountain Minnow | Compatible | No conflicts found |
| Zebra Danio | Compatible | No conflicts found |
| Amano Shrimp | Caution | Harlequin Rasbora may eat baby Amano Shrimp. Adults are usually safe, but expect fewer shrimplets. |
| Angelfish | Caution | Angelfish can bully smaller, peaceful Harlequin Rasbora. |
| Bamboo Shrimp | Caution | Harlequin Rasbora may eat baby Bamboo Shrimp. Adults are usually safe, but expect fewer shrimplets. |
| Betta | Caution | Betta can bully smaller, peaceful Harlequin Rasbora. |
| Black Skirt Tetra | Caution | Black Skirt Tetra can bully smaller, peaceful Harlequin Rasbora. |
| Blood Parrot Cichlid | Caution | Blood Parrot Cichlid can bully smaller, peaceful Harlequin Rasbora. |
| Boesemani Rainbowfish | Caution | Harlequin Rasbora and Boesemani Rainbowfish only share 81–82°F. That's a tight window. |
| Cherry Shrimp | Caution | Harlequin Rasbora may eat baby Cherry Shrimp. Adults are usually safe, but expect fewer shrimplets. |
| Crystal Red Shrimp | Caution | Harlequin Rasbora may eat baby Crystal Red Shrimp. Adults are usually safe, but expect fewer shrimplets. |
| Dwarf Gourami | Caution | Dwarf Gourami can bully smaller, peaceful Harlequin Rasbora. |
| Electric Blue Acara | Caution | Electric Blue Acara can bully smaller, peaceful Harlequin Rasbora. |
| Electric Yellow Lab | Caution | Electric Yellow Lab can bully smaller, peaceful Harlequin Rasbora.; Harlequin Rasbora (pH 5–7.5) and Electric Yellow Lab (pH 7.7–8.6) prefer different pH. |
| Endler's Livebearer | Caution | Harlequin Rasbora (1–12 dGH) and Endler's Livebearer (15–35 dGH) prefer different water hardness. |
| Fancy Goldfish | Caution | Harlequin Rasbora and Fancy Goldfish only share 70–70°F. That's a tight window. |
| Firemouth Cichlid | Caution | Firemouth Cichlid can bully smaller, peaceful Harlequin Rasbora. |
| Forktail Blue-eye | Caution | Harlequin Rasbora (1–12 dGH) and Forktail Blue-eye (15–30 dGH) prefer different water hardness. |
| German Blue Ram | Caution | Harlequin Rasbora and German Blue Ram only share 81–82°F. That's a tight window. |
| Ghost Shrimp | Caution | Harlequin Rasbora may eat baby Ghost Shrimp. Adults are usually safe, but expect fewer shrimplets. |
| Kissing Gourami | Caution | Kissing Gourami grows 6× longer than Harlequin Rasbora and may treat it as food.; Kissing Gourami can bully smaller, peaceful Harlequin Rasbora. |
| Molly | Caution | Harlequin Rasbora (1–12 dGH) and Molly (15–30 dGH) prefer different water hardness. |
| Mystery Snail | Caution | Harlequin Rasbora (pH 5–7.5) and Mystery Snail (pH unknown) prefer different pH.; Harlequin Rasbora (1–12 dGH) and Mystery Snail (unknown dGH) prefer different water hardness. |
| Nerite Snail | Caution | Harlequin Rasbora (pH 5–7.5) and Nerite Snail (pH 8–8.4) prefer different pH. |
| Paradise Fish | Caution | Paradise Fish can bully smaller, peaceful Harlequin Rasbora. |
| Pictus Catfish | Caution | Pictus Catfish can bully smaller, peaceful Harlequin Rasbora. |
| Rainbow Shark | Caution | Rainbow Shark can bully smaller, peaceful Harlequin Rasbora. |
| Red-Tail Shark | Caution | Red-Tail Shark can bully smaller, peaceful Harlequin Rasbora. |
| Three-spot Gourami | Caution | Three-spot Gourami can bully smaller, peaceful Harlequin Rasbora. |
| Variatus Platy | Caution | Harlequin Rasbora (1–12 dGH) and Variatus Platy (14–30 dGH) prefer different water hardness. |
| Yoyo Loach | Caution | Yoyo Loach can bully smaller, peaceful Harlequin Rasbora. |
| Chinese Algae Eater | Avoid | Chinese Algae Eater grows 6× longer than Harlequin Rasbora and may treat it as food.; Chinese Algae Eater is aggressive toward tankmates. Harlequin Rasbora is peaceful. |
| Convict Cichlid | Avoid | Convict Cichlid is aggressive toward tankmates. Harlequin Rasbora is peaceful. |
| Iridescent Shark | Avoid | Iridescent Shark eats small fish, and Harlequin Rasbora only grows to about 2.1 in. |
| Oscar | Avoid | Oscar eats small fish, and Harlequin Rasbora only grows to about 2.1 in. |
Care notes
Needs: Dim lighting and planting (Microsorum, Cryptocoryne, Anubias); regular small live/frozen foods alongside dried food
Group: SF: group of at least 8-10
Temperament: peaceful toward other fish, peaceful toward its own kind. Lives in the middle of the tank.
Common questions
How big does a Harlequin Rasbora get?
About 2.1 inches (4.5 cm SL) as an adult, according to seriouslyfish.com.
What size tank does a Harlequin Rasbora need?
At least 24 inches long and about 14 gallons. The smallest standard tank that meets that is a 20 gallon long.
How many Harlequin Rasboras should be kept together?
At least 8. SF: group of at least 8-10
What fish can live with a Harlequin Rasbora?
Species that passed every check include Neon Tetra, Cardinal Tetra, Ember Tetra, Chili Rasbora, Celestial Pearl Danio, Cherry Barb.
Gear for a Harlequin Rasbora setup
TankSmallest standard tank that meets its minimum: 20 gallon long (30 in long).Find on Amazon →HeaterAbout 100 W for 20 gallons, holding 70–82°F.Find on Amazon →FoodMeaty frozen foods suit its diet.Find on Amazon →Test kitCheck ammonia, nitrite and pH. Cycle the tank before adding fish.Find on Amazon →
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Related guides
Sources
Values come from these pages, in our own words. Status: researched from source pages. Last reviewed 2026-10-12.
- seriouslyfish.com /species/trigonostigma-heteromorpha/
- fishbase.se /summary/Trigonostigma-heteromorpha.html