Fish stocking calculator
Bioload, schooling minimums, compatibility warnings, and a weekly water change estimate for any freshwater roster.
Add fish above to start building your tank.
Add plants above (optional).
- Temp
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- pH
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- Hardness
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- Add fish to see compatibility findings.
Add at least one fish to your roster, then we'll suggest tankmates and plants that fit.
What this calculates
Each species carries a bioload coefficient, calibrated so a neon tetra is 1 and everything else scales from there by adult mass and how messy the fish eats. Your tank's capacity comes from its volume, with multipliers for planting, filtration, and water change habit. The percentage is roster load over capacity.
Schooling species get flagged under their group minimum. The floor per species comes from the profile data, not a blanket "six of everything": some tetras are fine at six, some barbs need eight or more before the nipping stops.
The compatibility rules cover the common ways a community goes wrong: no overlapping temperature, pH or hardness window; a tank too small or too short for a species; fin nippers with long-finned fish; predators a third bigger than their tankmates; aggressive fish next to small peaceful ones; two territorial cichlids in one tank; shrimp with shrimp eaters; surface breathers in tall narrow tanks. Footprint matters for the length and surface rules, not only volume.
What this doesn't do
It doesn't know the individual fish. A betta that ignores tetras and one that hunts them are the same species to the tool. Treat every warning as a reason to watch the tank, not a verdict, and treat a clean result as a starting point.
It doesn't model growth. Coefficients are for adults, so a tank of juveniles will read heavier than it feels today and lighter than it will in a year.
Related tools
- Tank volume - Measure your tank if you haven't already.
- Planted tank planner - Match plants to your fish roster.