Aquarium Tank Size & Stocking Calculator
Enter your tank dimensions and the average adult size of your fish to estimate safe stocking levels and total tank volume for a healthy aquarium.
Recommended Max Fish Count
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Tank Volume (gallons)—
Adjusted Inches of Fish Allowed—
Average Fish Length Used (in)—
About this calculator
Estimate safe fish stocking levels and required tank volume based on the inches-per-gallon rule and tank dimensions.
Frequently Asked Questions
What is the inches-per-gallon rule?
A common freshwater guideline suggests roughly 1 inch of adult fish length per gallon of water, though it's a rough starting point, not a strict rule.
Why does bioload matter?
Some species produce more waste relative to their size (like goldfish or plecos), requiring more filtration capacity and effectively lowering safe stocking density.
Does this account for filtration or plants?
No, this is a simplified estimate. Strong filtration, live plants, and regular water changes can allow for higher stocking than the basic guideline suggests.