Aquarium filter flow & turnover calculator

Divide delivered flow per hour by actual aquarium water volume. A filter delivering 130 US gallons per hour to 29 US gallons produces about 4.48 turnovers per hour. Liters and US gallons give the same ratio when both values use matching units.

Turnover is a rate, not a guarantee that every parcel of water passes through the media equally. Intake placement, outlet direction, rockwork, plants, and short-circuiting can leave low-flow zones even when the arithmetic looks strong.

A pump performance curve relates flow to delivery head. Vertical lift, tubing diameter and length, bends, valves, intake guards, filter media, and fouling can all change the operating point. Some filter makers publish both pump output and filter circulation under specified conditions; use the figure that best matches the installed system.

There is no single reduction percentage that fits every filter. The 65% default is provided only to reproduce a common rough estimate and remains editable. A pump curve or direct measurement is stronger evidence.

When it is safe for the equipment, collect outlet water for a measured number of seconds, measure the collected volume, and scale it to one hour. For example, 5 liters collected in 30 seconds equals 600 liters per hour. Follow the equipment instructions and never run a pump dry.

Measure under normal operating conditions with the usual media, water level, hoses, spray bar, and valves. Repeat the measurement after maintenance to see whether cleaning restored output.

Filter turnover describes water processed by a filter or moved through a sump. Display circulation describes movement inside the aquarium, which can be produced by filter returns, powerheads, wavemakers, air-driven lift, and other pumps.

Reef systems often use much higher total circulation than sump throughput. Adding powerhead flow to a filter target or sizing a sump return to a coral-flow number can produce a misleading equipment plan.

Very high or poorly directed flow can stress fish, flatten plants, move substrate, expose corals to an unsuitable pattern, increase noise, exceed overflow capacity, or push water past media too quickly. Watch the aquarium after changing flow rather than relying on a ratio alone.

A lower-than-planned result also does not automatically mean a larger filter is required. Check blockage, hose routing, valves, impeller condition, water level, media packing, and maintenance history first.