Pet

Fish Tank Stocking (Rough) Calculator

Roughly estimate total fish length a tank can support using the inch-per-gallon guide.

This rough guide shows the total adult fish length, in centimetres, that the tank volume entered can support under the one-inch-per-gallon rule.

Formula

Total fish length in centimetres equals US gallons multiplied by 2.54, from the one-inch-per-gallon rule.

How it works

Tank litres convert to US gallons, and each gallon is allowed one inch of adult fish length. The rule ignores species behaviour, waste, filtration and shape, so it is only a first sanity check.

Worked example

For example, 100 litres is about 26.4 US gallons, and 26.4 × 2.54 = about 67 cm of total adult fish length.

FAQs

Should I stock to this limit?
Stay below it, especially as a beginner; filtration and maintenance matter.

Does adult size count?
Yes. Always use adult size, not the size at purchase.

Do plants change it?
Plants help water quality but do not make the rule exact.

General information only, not veterinary advice.

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