Equipment Guides
What Size Filter Does My Aquarium Need?
Learn how to size an aquarium filter by turnover (litres per hour), why rated flow is misleading, and how to match filtration to your tank and fish.
Read more →Aquarium Filter Flow Calculator
Community (4-6x)
400-600
LPH
106-159 GPH
Recommended
500
LPH (5x turnover)
Heavy / messy (10x)
1000
LPH
264 GPH
Rated flow is measured with an empty filter, so choose one rated 10 to 20 percent above your target.
Find the right filter flow rate for your aquarium. Enter your water volume and the calculator shows the recommended turnover in litres and gallons per hour, from gentle to heavily stocked tanks.
How much filter flow do I need?
Filters are rated by flow, the volume of water they move each hour. A healthy aquarium turns its whole volume over about 4 to 6 times per hour, and messy or heavily stocked tanks benefit from up to 10 times. Multiply your water volume by the turnover to find the flow you need. Manufacturer ratings are measured with an empty filter, so choose a filter rated a little above your target to allow for media and hose resistance.
Filter flow rate by tank volume
| Litres | Flow (4–6× per hour) (L/h) | Flow (4–6× per hour) (GPH) | Maximum (10×) (L/h) |
|---|---|---|---|
| 20 | 80–120 | 21–32 | 200 |
| 40 | 160–240 | 42–63 | 400 |
| 60 | 240–360 | 63–95 | 600 |
| 100 | 400–600 | 106–159 | 1,000 |
| 150 | 600–900 | 159–238 | 1,500 |
| 200 | 800–1,200 | 211–317 | 2,000 |
| 300 | 1,200–1,800 | 317–476 | 3,000 |
Calculated with the same formula as the calculator above. Values are rounded.
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Frequently asked questions
What flow rate filter do I need?
Aim for 4 to 6 times your tank volume per hour for a community tank, and up to 10 times for heavily stocked or messy fish. Enter your volume above to see the range in litres and gallons per hour.
What does turnover mean for a filter?
Turnover is how many times the filter moves the entire tank volume in one hour. A 100 litre tank with 5 times turnover needs about 500 litres per hour of flow.
Is more filter flow always better?
Not always. Strong flow suits messy fish and rivers species, but bettas, fancy goldfish and calm-water fish prefer gentler flow, which you can reduce with a spray bar.
Should I trust the filter's rated flow?
Rated flow is measured with an empty filter, so real flow is lower once media and hoses are fitted. Choose a filter rated 10 to 20 percent above your target.
How much filtration for a goldfish tank?
Goldfish are messy, so aim for the higher end, around 6 to 10 times turnover per hour, with strong biological media.
Can a filter be too powerful?
Yes. If fish are pushed around or struggle to swim, reduce the flow with a spray bar, flow deflector or by adjusting the outlet.
Related guides
Learn the core ideas behind fish tank volume before or after using the calculator.
Maintenance Guides
How to Clean a Fish Tank Without Killing the Bacteria
A simple aquarium cleaning routine: how much water to change, how to vacuum gravel and clean the glass without harming your filter bacteria or stressing fish.
Read more →Setup Guides
How to Cycle a Fish Tank (Before You Add Fish)
Cycling a new aquarium builds the bacteria that keep fish safe. The nitrogen cycle explained simply, plus a step-by-step fishless cycle.
Read more →