FishMaths

Stocking calculator

Add the fish you have or want. You'll get a rough bioload estimate and warnings for fish that need a bigger tank or a bigger group.

    Result
    0
    Enter your numbers

    How the math works

    Each fish counts its adult length, weighted by body shape and waste. Slim fish like tetras count less than chunky, messy fish like goldfish and plecos. That total is compared to your tank volume, adjusted for filtration. It is a rough guide, not a rule.

    Is the inch per gallon rule accurate?
    Not really. It ignores body shape, waste and behavior. This calculator weights each fish differently, but temperament, swimming space and water parameters matter just as much.
    Why does it warn about group size?
    Schooling fish kept in small groups get stressed, hide, and can get sick more often. Groups of six or more are a common recommendation.
    Does this check if fish get along?
    No. Always research compatibility, temperature and pH needs before mixing species.