Fish Stocking Calculator
Estimate a safe stocking level for your tank to avoid overcrowding.
How it works
A common guide is 1 cm of adult fish length per litre is far too high; a safer modern guideline is roughly 1 cm of slim-bodied fish per 2 litres of actual water, adjusted down for messy or large-bodied fish and up for heavy filtration and live plants.
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Formula & Method
A common guide is 1 cm of adult fish length per litre is far too high; a safer modern guideline is roughly 1 cm of slim-bodied fish per 2 litres of actual water, adjusted down for messy or large-bodied fish and up for heavy filtration and live plants.
Example Calculation
A 100 L planted tank with good filtration could hold ~12-15 small tetras (≈3 cm each) plus a small clean-up crew, leaving a safety margin for water quality.
Frequently Asked Questions
Is the 1 inch per gallon rule reliable?
No, it's outdated and ignores body mass, waste output and swimming needs. Use it only as a rough ceiling and stock conservatively.
What increases stocking capacity?
Strong biological filtration, live plants, frequent water changes and a larger tank footprint all raise safe stocking levels.