Aquarium Stocking Calculator
How many fish your tank can hold.
Instant results
1
Enter your pet's details
Auto-fill from:Save a pet profile
?
How this is calculated
Uses the traditional 1 inch of adult fish per US gallon (≈1 cm per 1.5 litres) guideline for small, slim tropical fish. It underestimates the needs of goldfish, cichlids and other heavy-bodied or messy species — research each species and use strong filtration.
Source-based educational tool; not independently reviewed by a veterinarian. Cited guidance does not imply endorsement by its authors.
Formula
Total fish length (cm) = litres ÷ 3.785 × 2.54 (1 inch per US gallon)
Assumptions
- •Small, slim tropical species
- •Adequate filtration and water changes
- •Rule of thumb, not a scientific standard
Sources
Traditional rule of thumb — no peer-reviewed source.