To your left you will see a wide range of Sub-Catergories of pumps and powerheads. We believe in good water flow for your tank, especially if it's a reef tank. There are many options for water flow.

Some quick basics:

Powerheads are generally used inside the tank, with systems without a sump or systems with a sump but wanting to add more flow.

Submersible pumps: These are pumps that can be fully submersed in saltwater. You can put them inside your sump or tank. Some can run out of the water as well.

External pumps: These are used outside your sump only. You install via a bulkhead from your sump to the pump, or with some up and over pipework and self-prime the pump. These pumps can not get wet. The main advantage to these type of pumps are durability and power. They have sizes for just about any size tank.