What does turnover rate mean?

Turnover is how many times the entire tank volume passes through circulation each hour. A turnover of 10x on a 200 litre tank means 2000 litres of water move per hour. It is the standard way to express how vigorously a tank is circulated, independent of tank size.

How much turnover does each tank type need?

Rough targets are 4 to 6x for planted tanks, 5 to 10x for fish-only and cichlid tanks, and 20 to 40x for reef tanks where corals need strong, varied flow. Reef figures usually combine a return pump with several powerheads or wavemakers rather than one giant pump.

Should I use my filter's rated flow as-is?

No. Manufacturer ratings are measured with an empty filter and no head height. Media, hoses, and lifting water above the tank cut real flow by 25 to 40 percent. Buy a pump rated meaningfully above your target so the in-tank flow still meets the number this tool gives.

Can a tank have too much flow?

Yes. Excessive flow stresses slow-swimming fish like bettas and fancy goldfish, blows substrate around in planted tanks, and prevents food from settling. Match flow to the livestock: high for reef SPS corals and rheophilic fish, gentle for labyrinth fish and shrimp.

Does the calculator account for head height?

The base result is the required in-tank flow. Because real pumps lose flow to head height and media, the tool also shows a suggested purchase rating about 35 percent higher so the delivered flow still meets your target after those losses.

Aquarium Flow & Turnover Rate Calculator

Good circulation keeps oxygen, heat, and nutrients evenly distributed and stops detritus settling. This calculator turns a target turnover rate into the concrete flow figure your filters and powerheads must deliver, and shows the right turnover band for your type of tank.

How it works

Required flow is simply volume multiplied by turnover:

flow per hour = tank volume × turnover (times per hour)

So a 200 litre reef tank at 25x turnover needs 5000 litres per hour of combined circulation. Because real pumps lose flow to media and head height, the tool also suggests a purchase rating about 35 percent higher than the in-tank target.

Recommended turnover and tips

Use roughly 4 to 6x for planted tanks, 5 to 10x for fish-only and cichlid setups, and 20 to 40x for reef tanks. In a reef, spread that across a return pump plus powerheads or wavemakers to create varied, turbulent flow rather than one laminar jet. Aim circulation to eliminate dead spots where detritus collects, and dial it back for slow-swimming or long-finned fish that struggle in strong currents.