Fish comparison
Harlequin Rasbora vs Penguin Tetra
How the Harlequin Rasbora and Penguin Tetra compare on care, size, water and temperament, and which fish suits your tank.
By Mike ElmiraUpdated
TL;DR, Harlequin Rasbora vs Penguin Tetra
The Harlequin Rasbora and the Penguin Tetra come up together a lot when people are choosing a fish, and they are close enough to weigh side by side. Both are happy somewhere around 22 to 28 °C and pH 5.8 to 7.5, so a single tank can suit either one. Neither is harder than the other to keep, so the choice comes down to look and stocking rather than skill. If tank space is tight, the Harlequin Rasbora needs less room to feel settled; give the Penguin Tetra the nod when you have the litres to spare.
Group compatibility overview
Excellent fit
Every key parameter overlaps and no major conflicts surfaced.
4 notes
Temperature
- Harlequin Rasbora22–28 °C
- Penguin Tetra22–28 °C
pH
- Harlequin Rasbora5.5–7.5
- Penguin Tetra5.8–7.5
Hardness
- Harlequin Rasbora2–12 dGH
- Penguin Tetra2–15 dGH
What to plan for
- Harlequin Rasbora schools, stock at least 8You've planned for 1 harlequin rasbora. Harlequin Rasbora need a group of at least 8 to feel safe and shoal naturally, below that they're stressed and lose colour. Dial up the count, or remove the species.
- Penguin Tetra schools, stock at least 8You've planned for 1 penguin tetra. Penguin Tetra need a group of at least 8 to feel safe and shoal naturally, below that they're stressed and lose colour. Dial up the count, or remove the species.
- No bottom teamNo bottom-dwelling fish or shrimp. A small group of corydoras or a shrimp colony picks up leftover food and keeps detritus in check.
- 67% of your fish swim in the midHeavy concentration in a single zone. Spreading stocking across all three levels makes the tank read fuller for the same bioload.
Full attributes
Every parameter, side by side| Parameter |  FishHarlequin RasboraTrigonostigma heteromorpha |  FishPenguin TetraThayeria boehlkei |
|---|---|---|
| Category | Fish | Fish |
| Origin | Thailand, Malaysia, Sumatra | Amazon basin |
| Family | Cyprinidae | Characidae |
| Temperature | 22–28 °C | 22–28 °C |
| pH | 5.5–7.5 | 5.8–7.5 |
| Hardness (dGH) | 2–12 | 2–15 |
| Flow rate | Low to Medium | Low to Medium |
| Min tank | 60 L | 90 L |
| Adult size | 4–5 cm | 5–6 cm |
| Difficulty | 1 / 5 | 1 / 5 |
| Lifespan | 5–8 yrs | 4–6 yrs |
| Diet | Omnivore | Omnivore |
| Water column | Mid | Mid to top |
| Schooling | Yes | Yes |
| Plant safe | Yes | Yes |
| Shrimp safe | Mostly (may eat shrimplets) | Yes (with adults) |
Frequently asked questions
Direct answers to the questions search engines and AI assistants surface most often about this species.
Can you keep Harlequin Rasbora and Penguin Tetra together?
Yes. Their temperature and pH ranges overlap around 22 to 28 °C and pH 5.8 to 7.5, so one set of water conditions keeps both comfortable. Match group sizes and cover the usual planted-tank basics and they share a tank fine.
Which is easier to keep, the Harlequin Rasbora or the Penguin Tetra?
They sit at the same care level, both very easy, so neither is the obvious beginner pick. The decision is really about the look you're after.
Do Harlequin Rasbora and Penguin Tetra need the same water?
Close to it. Aim for 22 to 28 °C and pH 5.8 to 7.5 and you're in the shared sweet spot for both. Full ranges are in the table above.
What's the main difference between the Harlequin Rasbora and the Penguin Tetra?
Space. The Harlequin Rasbora wants about 60 litres minimum and the Penguin Tetra around 90, so tank size can settle it.