Aquarium Stocking Calculator

It is a rough guideline that allows about 1 inch of adult fish length per gallon of freshwater. This tool uses 1 inch per gallon for freshwater and a more conservative 0.5 inch per gallon for saltwater.

It is only a rough ballpark. Bioload depends far more on species, body shape and mass than on length alone, so one tall or messy fish can equal several thin ones of the same length. Research each species before stocking.

Saltwater systems usually have lower oxygen capacity and a smaller margin for error in water chemistry, so a lighter stocking level helps keep parameters stable. That is why this tool uses 0.5 inch per gallon for saltwater.

Use a realistic net volume. Gravel, rock, sand and equipment displace water, so the actual volume is often 10 to 15 percent below the rated tank size. Stocking to net volume keeps you on the safe side.

Yes. Strong filtration, live plants and frequent water changes raise the load a tank can handle, while weak filtration lowers it. Always cycle a new tank fully and watch your water parameters as you add fish.