An aquarium powerhead can be used to create water flow within an aquarium but may also be used for a variety of other purposes. You can use a powerhead as a return pump for aquarium filter systems, like sumps. A powerhead pump can also provide water flow to your media reactor, chiller or UV sterilizer.
Connecting multiple fish tank powerheads to an aquarium controller will give you the ability to create more ocean-like water movement, such as random flow patterns, currents or tides. Some of the more sophisticated aquarium powerheads, like the EcoTech VorTech and Maxspect Gyre, include their own controller so you can fine-tune the water movement in your aquarium to eliminate dead spots and keep fish and coral happy.