Aquarium stocking calculator

Choose freshwater or saltwater, enter tank volume, and add fish from the Aquarium Tracker species catalog. The calculator starts with each species' maximum listed adult size and increases the allowance as fish become larger. Goldfish receive a separate, higher allowance.

The percentage is an Aquarium Tracker planning heuristic, not an industry-standard bioload measurement or a minimum-tank recommendation. Optional filter flow can reduce the estimate when turnover is low, but high flow never increases the tank's guide capacity.

Fish with the same length can have very different body mass, activity, feeding, waste production, and territorial behavior. Aquarium shape, surface area, oxygenation, plants, hardscape, filter media, and maintenance also change what a tank can support.

For that reason, the percentage is a comparison guide rather than a biological limit. Stock conservatively and add fish gradually only after behavior, ammonia, and nitrite remain stable. If conditions deteriorate, pause further additions and address the cause.

The calculator compares broad temperature, pH, temperament, and adult-size differences. It does not contain a complete pair-by-pair compatibility matrix and cannot predict how individual fish will behave.

Before purchasing, check minimum tank dimensions, group size, sex ratio, territory, diet, flow, substrate, and whether a larger species may eat a smaller one. A reputable aquarium shop or experienced aquatic specialist can help review the exact combination available to you.

A result below 70 percent is the calculator's lower estimated-load band. Between 70 and 90 percent is moderate, 90 to 100 percent leaves little buffer, and a result above 100 percent means the list should be reduced or reviewed carefully.

Do not aim for 100 percent simply because the calculator permits it. New tanks, inexperienced keepers, delicate fish, territorial species, and inconsistent maintenance all benefit from a larger buffer.