Methodology

We show our work. Every calculator exposes its formula, and our “real-tank” figures come from a transparent, documented dataset — not opinion.

Stocking calculator

Each species in our database has a bioload value — a unit of biological waste load per adult fish, tuned against community norms and adult body mass. We sum the bioload of every fish you add and divide by your tank volume in US gallons to produce a stocking % (~100% = fully stocked). We deliberately reject the “1 inch of fish per gallon” rule because it ignores adult size, waste output and swimming space. Filtration % compares your filter’s GPH to a ~4× turnover target. We also flag minimum tank size, schooling minimums, temperament conflicts and non-overlapping temperature ranges.

Volume calculator

Rectangular: length × width × height (inches) ÷ 231 = US gallons. Cylinder: π × radius² × height ÷ 231. Litres = gallons × 3.785. Filled weight ≈ 10 lb per gallon.

Real-tank dataset

Our “based on N real tanks” figures are aggregated from public posts and comments on r/Aquariums, r/PlantedTank, r/bettafish and r/shrimptank. We extract stated tank sizes, species, counts and water parameters, clean obvious errors, and report the median of stated values with the sample size (N). These are a real-world sanity range, not a prescription — always confirm requirements for your specific species and water.

Data is refreshed periodically; species database and sample sizes are expanding. Found an error? Tell us.