Aquarium Filter Size Calculator
An undersized filter is one of the most common causes of cloudy water and ammonia problems — this calculator works out the flow rate your tank actually needs, based on tank volume and how heavily it's stocked, then shows real filters from our full filter range that match.
Aquarium Filter Size Calculator
Work out the filter flow rate you need, and see real filters that match it.
Frequently Asked Questions
Why does tank type change the flow rate needed?
A standard freshwater community tank, a heavily stocked or messy tank (goldfish, cichlids), and a marine/reef tank all produce different amounts of waste, so each is sized against a different turnover multiple of the tank's total volume per hour.
Why do I need to choose a filter type as well?
Most aquarium keepers have already decided internal, external/canister, or hang-on based on their tank and stand setup before they start thinking about flow rate, so recommendations are scoped to the type you pick rather than mixing all three together. If you haven't decided yet, choose "Not sure / show me all" to compare across every type.
Is this the same as total water circulation in a marine/reef tank?
No — this calculator sizes the FILTER specifically. Reef tanks typically also run separate powerheads or wavemakers for total in-tank water movement, which is a different requirement to filter turnover and isn't covered here.
Do I need to tell you which fish I'm keeping?
No — this calculator works from broad tank-type categories only, not individual fish species or stocking counts, since precise stocking advice depends on far more than flow rate alone.