Aquarium Tank Volume Calculator
Estimate real water volume after substrate and waterline gap. This helps size filters, heaters, fertilizers, and water changes.
The result is an estimate. Hardscape, filters, and decorations reduce water volume further.
How to use the aquarium volume result
Real aquarium water volume is often lower than the advertised tank size. Substrate, waterline gap, hardscape, internal filters, and decorations all take up space. Use this result when sizing heaters, filters, water changes, fertilizer dosing, dechlorinator, and medication.
Aquarium tank volume FAQ
Why is real aquarium water volume lower than tank size?
Substrate, waterline gap, rocks, driftwood, filters, and equipment all reduce the actual water volume compared with the outside glass dimensions.
Should I dose fertilizer based on gross or real volume?
Use the best estimate of real water volume when dosing fertilizers, conditioners, or medicine. It is safer than using the advertised tank size.
How much water should I change weekly?
Many freshwater aquariums use 20% to 40% weekly water changes. Heavily stocked tanks, new tanks, or high-tech planted tanks may need a different routine.