Aquarium Air Pump Size Calculator – What Size Air Pump

Use the free Aquarium Air Pump Size Calculator below, right in your browser. No sign-up, no software to install, and nothing is sent to a server.

An air pump pushes air through stones or sponge filters, and the bubbles do two jobs at once. They stir the water surface so oxygen can enter, and they drive water through sponge filters so bacteria can clean it. A pump that is too weak leaves dead spots and a struggling filter, while a pump that is far too strong can stress fish with violent current. This calculator sizes the pump from tank volume and depth.

Enter your tank volume in litres and the depth of the water in centimetres. The tool estimates the air flow you need in litres per hour and suggests how many standard air stones that flow can feed. Deeper tanks get a higher figure, because the pump must push against greater water pressure, and deep tanks need more power to deliver the same bubbles at the bottom.

The rule used here is about half a litre of air per hour for each litre of tank water, with a thirty percent uplift when the depth passes sixty centimetres. A one hundred litre tank at forty centimetres deep therefore needs about fifty litres per hour, while a four hundred litre tank at eighty centimetres deep needs about two hundred and sixty litres per hour. These are starting points for a normally stocked tank, not hard limits.

Depth matters more than most buyers expect. Pump boxes often quote a headline flow measured with almost no back pressure, but a stone sitting sixty centimetres down is a different job. If your tank is deep, buy a pump rated for that depth, or check the flow curve if the maker publishes one. A pump that wheezes at depth will still make noise while delivering very little air where it counts.

Air stones are rated by the flow they can spread evenly. This calculator allows about two hundred litres per hour per stone, so a large pump feeding one small stone will blast a narrow column of bubbles instead of a gentle spread. Split the airline with a gang valve when you need two stones, and place them apart so each end of the tank gets movement. Two gentle stones beat one violent stone in most community tanks.

Sponge filters change the maths slightly, because they need steady flow to pull water through the sponge. If your air pump drives a sponge filter, size for the filter first and treat surface movement as a bonus. A sponge that barely bubbles is barely filtering, and waste will build up in the sponge rather than being processed. Watch the bubble rate for a week after setup, because new sponges clog faster as bacteria colonise them.

Stocking level also shifts the real need. A heavily stocked tank, a tank with large messy fish, or a warm tank all use oxygen faster, because warm water holds less dissolved oxygen. In those cases, round up to the next pump size rather than down. The cost difference is usually small, and a valve lets you turn a strong pump down, while no valve can make a weak pump stronger.

Noise is a practical part of pump choice that numbers alone do not capture. Place the pump on a soft pad, keep it above the water level when possible, and fit a check valve so water cannot siphon back during a power cut. A pump sitting on a hollow cabinet will hum through the whole room, while the same pump on a folded towel may be nearly silent. Check valves are cheap, and they protect both the pump and your floor.

Airline layout deserves a minute of thought. Long thin airline loses pressure, and every extra splitter or sharp bend costs flow. Keep runs short, use the correct diameter tubing for your pump, and replace tubing that has gone hard or yellowed, because stiff tubing leaks at the joints. If one stone bubbles strongly and another barely moves, the problem is usually a kink, a leak or an unbalanced valve, not the pump itself.

Finally, remember that an air pump supports oxygen levels but does not replace water changes or filtration. Test your water regularly, keep stocking sensible, and watch the fish: gasping at the surface, hanging near the filter outlet or faded colours can all point to low oxygen or poor water quality. Use this calculator to buy the right pump, then confirm with your eyes and your test kit that the tank is genuinely comfortable.

Versión en español: Tamaño de bomba de aire para acuarios – Caudal según profundidad