Choosing a Main Return Pump
There are two main types of water pumps used in aquariums: utility pumps and circulation pumps. Circulation pumps circulate water inside the aquarium to replicate ocean waves and tides. Utility pumps are pumps with a hose connection used to supply water to various gear and equipment. Your main return pump is the utility pump that supplies water to your filtration sump or back filtration compartment in an all-in-one aquarium. We have a section of External Main System Aquarium Water Pumps. All of these pumps are external pumps. The Reef Octopus Controllable Pumps, Tunze Silence and Hydor Seltz Pumps can be used externally or submersed in a sump. For smaller aquariums we also have a section of submersible pumps that could be a main utility return pump.

Here is a list of the steps to follow when selecting a return pump.

Pick the Right Flow Rate
We recommend a flow rate of at least 3-4 times tank turnover per hour through your aquarium’s return pump. It is important to note that the total circulation turnover rate should be higher than this. We recommend at least 10 times tank volume in total circulation for reef aquariums. This does not all have to go through the return pump. With four-times system turnover, all of the water in the tank passes through the filtration 96 times per day. Increasing the return pump size beyond 4 times turnover starts to have diminishing returns. Additionally, large return pumps can be expensive and loud, so we recommend sticking to the 3-4 times an hour rule. The rest of your total tank circulation can be handled with dedicated circulation pumps.

Pump Head Pressure
When picking out the correct size pump, you need to consider what flow the pump will provide after you have connected your tubing and any additional equipment, such as a chiller or UV sterilizer. The farther the pump has to push the water, and the more bends in the tubing, the less the flow will be once the water finally gets back to your main display.

The resistance from the plumbing and gear connected to a pump is called head pressure. The greater the head pressure, the lower the actual flow rate of the pump will be. Most manufacturers produce a flow rate chart showing how a pump's performance is affected by head pressure. Iwaki, for example, has some very helpful charts. The Iwaki America chart on the right shows how much flow you will get with their pumps with each given amount of head pressure. Each foot the water needs to rise is one foot of head pressure. Bends and long horizontal tubing, as well as filter material and any reduction in hose/pipes, will create head pressure.

Head pressure is very important for unique installs where the sump is in the basement while the tank is on the first or second story of the house. For most aquarists, keeping head pressure in mind may simply mean getting a pump one size larger than you would initially think. For example, if you wanted to get 600 gph of turnover you should probably get an 800 gph pump because after the head pressure loss you will be getting closer to 600 gph flow.

External or Internal Pumps?
There are two ways to install a return pump: externally and internally. Internal pumps sit inside of the aquarium sump or sit in an all-in-one compartment with a hose attached that runs back to the main display. External pumps sit next to the sump with one plumbing line from the sump to the pump’s inlet and a second plumbing line from the pump’s outlet to the main display tank.

External pumps have some advantages. They transfer less heat to the aquarium water, and they generally stay cleaner than a totally submerged pump, but we recommend internal pumps to the majority of customers. Internal pumps are far less likely to leak. There is less plumbing involved, and because the plumbing is in the filtration area, even if you don’t tighten everything properly, the water will drip back into the sump. For some large systems, the only option may be an external pump.

AC or DC Pumps?
AC pumps plug directly into the wall, while DC pumps have a power brick that converts wall power to DC. The power brick is similar to the charging brick with a laptop computer. For more information on AC pumps vs. DC pumps, check out our article Why Use a DC Aquarium Return Pump. With return pumps of less than 800 gallons per hour, the energy savings and noise reduction of a DC pump are barely noticeable. But for larger pumps, the energy savings and noise reduction can make a big difference. We would go with a DC pump for any large return pump.

Installation Tips
Here are a few installation tips when installing return pumps.

• Use squishy stuff. Use soft plumbing, such as flexible hose, to connect to your pump. Setting your pump on a soft surface, such as suction cups or a rubber mat, will reduce pump noise caused by vibrations.
• Make your line as short as possible. Return lines longer than necessary will increase head pressure and reduce pump performance. Keep your plumbing lines as short as possible.
• Use as few fittings as possible. Each plumbing fitting is another potential leak point, and each bend increases head pressure and reduces pump flow. Keep the return plumbing as simple as possible.
• Use true unions for external pumps. True Unions are designed to connect to an external pump and allow you to shut off the water and remove the pump without flooding your floor. They are essential to any external pump installation.
• Use hose clamps on every tubing connection. Even if the tubing fits snugly over a hose barb, always add a hose clamp to prevent the tube popping off. Use plastic clamps for submerged connections and metal clamps for dry connections.

Backup Pump
The return pump is a very important piece of equipment. If your return pump stops working, then none of your filtration gear will work. We recommend keeping a backup pump on hand. Your backup pump doesn’t need to be as powerful, quiet, or energy-efficient as your main return pump, but we do recommend keeping the plumbing connections the same as your main return pump. As long as the plumbing connections are identical, a backup pump can be quickly swapped for your main return pump, giving you some time to fix the problem. A used pump or a basic, affordable AC return pump is perfect as a backup.