Online Tool Store
Fish Pond Stocking Calculator
Estimate a safe stocking level for a garden or farm pond from volume, filtration, aeration, and the species you intend to keep.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
Fun & Misc
Fish Pond Stocking Calculator
Frontend preview — no upload or external service.
Stocking guidance
8,000 litres with good filtration supports roughly 8 to 10 adult koi — well under the volume-only rule, because adult koi reach 60 cm and load the filter heavily.
How the Fish Pond Stocking Calculator works
- Measure the pond volume rather than estimating it; depth is usually overestimated.
- Choose the species and be honest about adult size, not the size at purchase.
- Match stocking to your filtration and aeration, then stock below the figure and increase slowly.
The method
Stocking limits come from biological load, not just water volume: fish produce ammonia in proportion to how much they eat, which scales with body mass.
practical guide: allow roughly 1,000 litres per adult koi in a well-filtered pond
A rule based on centimetres of fish per litre fails for large species because waste output scales with mass, and a 60 cm koi outweighs six 10 cm fish many times over.
FAQ
Why do centimetre-per-litre rules fail?
Because waste scales with body mass, which grows roughly as the cube of length. Ten small fish and one large fish of the same total length are not equivalent loads.
What limits stocking first?
Usually oxygen on hot nights, then filter capacity. Both are worst in the early hours of a summer morning, which is when overstocked ponds lose fish.
How fast can I add fish?
Slowly. A filter's bacterial population grows to match the load, so adding a large batch at once outpaces it and causes an ammonia spike.
How we compare
| Feature | Online Tool Store | Doing it by hand | A single-purpose app |
|---|---|---|---|
| Accounts for filtration | ✓ | Rule of thumb | Yes |
| Adult size, not purchase size | ✓ | ✗ | ✓ |
| No account | ✓ | ✓ | ✗ |
| Water testing | ✗ | ✗ | ✓ |
Fish Pond Stocking Calculator sizes to adult fish and filter capacity, because the volume-only rules of thumb fail badly for large species.