Fish Tank Stocking Calculator
Bioload-based stocking guidance, not the oversimplified 1-inch-per-gallon rule.
Estimated bioload
45%
understocked
Bioload-based: it weighs adult size and waste output, not the oversimplified "1 inch per gallon" rule.
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How bioload works
Stocking isn't about total fish length; it's about waste. Every fish adds ammonia; your biological filter and water changes remove it. Larger, messier species (goldfish, cichlids, plecos) carry a much heavier bioload per inch than small, tidy schoolers (tetras, rasboras). This calculator weighs adult size and waste output, and flags fish that are below their minimum tank size or schooling group.
By species
Frequently asked questions
Why not just use 1 inch per gallon?
That rule ignores body mass and waste output. A 10-inch pleco produces far more waste than ten 1-inch tetras. Bioload-based estimates weigh adult size and how messy a species is, plus its minimum tank size and schooling needs.
What stocking percentage is safe?
Under about 85% leaves comfortable headroom; 85–100% is full and needs strong filtration and regular water changes; over 100% is overstocked.
Does filtration change how much I can stock?
Yes. Strong biological filtration and frequent water changes let a tank carry more, but minimum tank size and territory needs still apply per species.
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