Harlequin Rasbora
Trigonostigma heteromorpha
Also sold as Harlequins
Synonyms Rasbora heteromorpha
Harlequin Rasbora (Trigonostigma heteromorpha) is a peaceful freshwater fish that reaches about 4.5 cm (1.8 in) and swims in open water in a shoal. It wants 72–81°F (22–27°C) and pH 5.5–7.5, is kept in groups of 6 or more, and needs a tank of at least 40 L (11 gal).
At a glance
| Type | Fish |
|---|---|
| Adult size | 4.5 cm (1.8 in) |
| Minimum tank | 40 L (11 gal) |
| Group size | 6 or more |
| Temperature | 72–81°F (22–27°C) |
| pH | 5.5–7.5 |
| Temperament | Peaceful |
| GH | 1–12 |
| Lifespan | 5–8 years |
| Eats shrimp | Shrimplets only |
Before it goes in
- Harlequin Rasbora needs at least 40 L (11 gal). The smallest size in this library that clears that is the 15 Gallon.
- Keep 6 or more. Below that it hides, colours down and is far more likely to be picked on.
- Adult shrimp are safe; shrimplets will be eaten, so a shrimp colony will not grow in the same tank.
- It holds at 72–81°F (22–27°C). That shares a window with Betta and Cherry Shrimp, but not with Discus.
- A group of 6 takes up roughly 61% of what a 15 Gallon will comfortably hold, so plan the rest of the stock around it.
What tank size does it need?
At least 40 L (11 gal). The smallest size here that clears it is the 15 Gallon.
How many should I keep?
6 or more. Fewer than that and it spends its time hiding instead of out in the open.
Will it eat shrimp?
Adults are safe, shrimplets are not. You can keep shrimp with it; you just will not get a growing colony.
What water does it want?
72–81°F (22–27°C), pH 5.5–7.5, GH 1–12.
How long does it live?
5–8 years in a tank that suits it. That is how long you are signing up for.
Good tank mates
- Tank mates from this library that share its temperature window, are peaceful and eat neither it nor its young: Cherry Shrimp, Goldfish, Bristlenose Pleco, Celestial Pearl Danio and Molly.
- Plants that hold up with it: Hygrophila corymbosa 'Siamensis', Water Sprite, Anubias nana 'Petite' and Cryptocoryne wendtii.
Often compared with
| Harlequin Rasbora | Lambchop Rasbora | Dwarf Spotted Rasbora | |
|---|---|---|---|
| Adult size | 4.5 cm | 3 cm | 2.5 cm |
| Min tank | 40 L | 40 L | 41 L |
| Group | 6+ | 8+ | 8+ |
| Temperature | 72–81°F (22–27°C) | 73–82°F (23–28°C) | 68–82°F (20–28°C) |
| Eats shrimp | Shrimplets only | — | Shrimplets only |
More livestock
Sources (8) · checked Sep 2026
- Group size, Minimum tanksplashyfishstore.com
- Mature tankapp-aquatic.com
- Mature tankaquariumcoop.com
- Minimum tankfishbase.se
- Group sizefishkeeper.co.uk
- What it eatsgarnelio.de
- What it eatsgarnelio.de
- en.wikipedia.org