Aquarium Stocking
Check how many fish your tank can support by the inch-per-gallon rule.
About Aquarium Stocking
Dividing tank gallons by each fish's adult length gives a rough ceiling, a simplified but widely used planning rule. Overstocking spikes waste and ammonia, so a quick estimate keeps the bioload in line with filtration.
Formula
Aquarium Stocking
Max fish = tank gallons / inches per adult fish
- inch-per-gallon
- Classic guideline, one inch of fish per gallon of water
Worked example
With the default values below, Aquarium Stocking returns Max Fish (rule of thumb) of 20. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Tank volumeminimum 1 gal
- 20 gal
- Adult fish sizeone of Small (1 in), Medium (2 in), Large (4 in)
- Small (1 in)
Results
- Max Fish (rule of thumb)
- 20
- Water Volume
- 75.7 L
- Advice
- High stocking; monitor water quality closely
Step by step
- 1Values used
- 2Aquarium Stocking
- 3Max Fish (rule of thumb)= 20
- 4Water Volume= 75.7 L
- 5Advice= High stocking; monitor water quality closely
Assumptions and limits
- The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 1 decimal place, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Aquarium Stocking calculated?
Max fish = tank gallons / inches per adult fish Dividing tank gallons by each fish's adult length gives a rough ceiling, a simplified but widely used planning rule.
Why does Aquarium Stocking matter?
Overstocking spikes waste and ammonia, so a quick estimate keeps the bioload in line with filtration.
What values do I need to enter?
This calculator takes 2 inputs: Tank volume, Adult fish size. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.