Tank calculator
How many ranchu fit?
Enter your tank or tub. The calculator checks both volume and surface area, because ranchu need room at the top more than depth below.
3adult ranchu, comfortably
| Water volume | |
| Surface area | |
| Limit by volume | |
| Limit by surface | |
| Weekly water change (40%) |
Rules used: 75 L for the first adult and 40 L for each additional, plus 900 cm² of surface per adult. Young fish are counted at half. Filtration and feeding can stretch or shrink these numbers; the result is a starting point, not a law.