How big of a power head do I need?
Some websites say that water should circulate around a tank at least four times an hour, so if you have a 100-gallon tank, then you need a filter and/or powerhead that can move 400 gallons per hour (GPH). In our experience, the ideal flow rate depends on the plants and animals in your aquarium because some species can’t handle strong current and may become sick from all the stress. If you see that your fish and foliage are being whipped around the tank, choose a less powerful filter or power head. You can also try dispersing the flow by adding a spray bar or directing the output into a wall to decrease the kinetic energy.
For more information, read our full article on water circulation.