Aquarium Stocking & Cycling Calculator
Works out whether a freshwater community tank is sensibly stocked, using bioload instead of the old "inch per gallon" rule. Enter the tank as length × width × height or as litres, say whether it is planted and how heavily it is filtered, then list the fish one per line as name, adult length in centimetres and how many. Each fish is scored against a 5 cm reference fish, scaled by the cube of its length — because waste output tracks body volume, a 10 cm fish pollutes about eight times as much as a 5 cm one, not twice. The tool reports the effective volume after substrate and decor, a stocking percentage with plain OK / caution / overstocked bands, how many more of your smallest species would still fit, a suggested weekly water change, and a week-by-week fishless cycling timeline so the filter is ready before any fish go in.
Read the full guide to this tool
Results
Notes
- Bioload scales with the cube of body length against a 5 cm reference fish, so a single large fish can outweigh a whole school of small ones — the reason "an inch of fish per gallon" badly overstocks tanks with big fish.
- The effective volume drops about 10 % for substrate, rock and decor, and rises with live plants (which consume nitrate) and with heavier filtration.
- Cycle the filter before adding fish: the six-week timeline follows ammonia up, then the nitrite spike, then nitrate building as the tank finishes an ammonia→nitrite→nitrate fishless cycle.
- This is an educational estimate for peaceful community fish; it ignores territory, schooling minimums, temperament and adult-only bioload — always check the needs of each species.
Related tools
Punnett Square Calculator
Genotype and phenotype ratios of a cross.
Bacterial Growth Calculator
Population from doubling time and elapsed time.
DNA & RNA Sequence Toolkit
Complement, transcription, translation and GC content.
Hardy-Weinberg Equilibrium Calculator
Allele and genotype frequencies in a population.
Michaelis-Menten Kinetics Calculator
Enzyme reaction rate from Vmax, Km and [S].
Chemical Equation Balancer
Balance any chemical equation to whole numbers.