How Many Guppy in a 40-Gallon Tank?
In a 40-gallon tank you can comfortably keep about 3–28 Guppy. As a schooling species, never keep fewer than 3.
Why
Stocking is driven by adult size and waste output, not just fish count. Guppy reaches about 2" with a moderate bioload, and needs 72–82°F water at pH 7–8.2. Always cycle the tank and test water before adding livestock.
| Adult size | 2" |
|---|---|
| Minimum tank | 10 gallons |
| Temperature | 72–82°F |
| pH | 7–8.2 |
| Temperament | Peaceful |
| Schooling | Yes — group of 3+ |
| Diet | Omnivore |
| Care level | Easy |
| Origin | Northeast South America (introduced worldwide) |