Do I need a power head?
A powerhead is simply a submersible water pump that sucks in water from the input and sprays out a powerful stream of water from the output. This device can be used to speed up water changes, create your own DIY filtration, and of course boost water circulation in your aquarium.
Water circulation is commonly discussed in the saltwater aquarium hobby in order to imitate the movement of waves, but not having enough flow can also be a problem in freshwater setups. Fish tanks (especially large ones) with lots of decorations or hardscape can develop dead zones where lots of debris collects and algae starts to grow. Increasing water circulation can help (a) stir up waste particles so they get collected by the filter, (b) evenly distribute nutrients for aquarium plants to consume, and (c) improve surface agitation so that fish have enough oxygen to breathe. Plus, some species like rainbow shiners and hillstream loaches are used to living in fast flowing rivers and may appreciate greater current in their environment.
For more information, read our full article on water circulation.