When choosing a water pump type and size, there are several factors to include in your decision:

• Filtration type - What type of filter system is best for the type of aquarium you are planning? The type of filter you choose dictates the type of water pump you need.
• Desired flow rate - Do the inhabitants of your aquarium require a greater flow rate (saltwater fish), or a lesser one (planted aquarium). Research the flow rate needs of the type of aquarium you are planning.
• Plumbing and head height - What type of plumbing will be installed? Are you using a lot of elbows or have sharp turns? Where will the filtration system be located? Directly underneath the aquarium? In the basement or another room? Be sure to consider the total distance the pump will be required to move your aquarium water.
• Additional devices - Will your new aquarium require additional filtration or temperature control devices, such as UV sterilizers, protein skimmers, chillers, etc.?

In addition to powering your filtration system and providing water movement in your aquarium, water pumps can also be used to power other devices such as protein skimmers, to drain or fill your tank, or even to mix up saltwater in holding tanks for water changes.

If you are looking for a pump to power your filtration system, there are two different types of pumps to consider: submersible and in-line. Some of the more versatile pumps can be used either submersed or in-line.

Submersible water pumps are run completely underwater, usually in the sump of a wet/dry filtration system. They draw water from the filter and push it back into the aquarium - or through other devices like chillers or UV sterilization units. There are several advantages to a submersible pump: they are easy to install because they don't require you to drill and install a bulkhead in your filter system and they tend to be a little quieter because they run underwater.

The main disadvantage with submersible pumps, especially the more powerful ones, is that they are water cooled, so that means unwanted heat may be added directly to your aquarium water. Additionally, your filter's sump may have limited space for a pump, so the dimension of the submerged pump is an important consideration.

In-line water pumps are used out of the water and are connected to an inlet hose and outlet hose used to filter your aquarium water. The major advantage of in-line pumps is that they are air-cooled, which means they may add less heat to the water. They are often more powerful pumps, able to move more gallons per hour. In-line water pumps can be installed in one of two configurations: pressure setups or free-flow setups. Some pumps are successfully used in either configuration. Other in-line pumps are optimized for one specific configuration.

NOTE: Very high head heights (6 or more feet) can create elevated levels of back pressure. Remember to consider head height when choosing your water pump.

• In-line pressure set ups - This type of configuration normally places the pump before a canister filtration system. The pump forces water under pressure into the canister system. Pumps configured in this type of setup receive a substantial amount of back pressure from the filtration device. Some in-line pumps are specifically built to handle back pressure with ease.
• In-line free-flow set ups - This type of configuration often places the pump after the filtration has already occurred, such as a wet/dry filter. The pump takes the filtered water from the sump and sends it back up into the aquarium or through additional devices such as an UV sterilizer or protein skimmer. Pumps configured in this type of setup receive very little back pressure. Therefore, they are often able to move more water with less effort. Some in-line pumps are specifically built for maximum efficiency in these low-pressure situations.