Choosing a Aquarium Water Pump
The critical choices when choosing a pump are:
- Powerhead or pump. A power head is submersible pump and a pump is an external pump. Some pumps, such as the Pondmaster pumps can be used submersed or externally.
- Connections. All of our pumps list the diameters of the input and outlets. You always want to use a pump with an outlet diameter that is equal to or less than the diameter of the hose and all other fittings before the water is returned to the tank or sump. For example, if you use 3/4" hose with a pump with a 1" output, you will severely restrict the flow of the pump.
- Flow rate. All of our pumps have the flow rate listed in gph (gallons per hour). The flow rate will be affected by the amount of head pressure. Consult the Head Pressure and Pump Performance section below for information on determining how much head pressure you will have.
Aquarium Water Pump Desired Flow Rate
The optimum tank "turnover rate" is approximately 6 to 7 times per hour for saltwater fish-only tanks, 10 to 12 times per hour for saltwater reef tanks and 4 to 5 times for freshwater tanks. For example, the pumps on a 50 gallon reef tank should be a total of 500 to 600 gph (after head pressure is taken into account). When determining which pumps you needs to achieve your desired flow rate you should include all the pumps in your system. This includes the powerheads in the tank and any pumps running power filters and canister filters. Although your protein skimmer pump may have significant flow, since protein skimmers have a great deal of head pressure you will not get much flow from your protein skimmer pump.
Aquarium Water Pump Head Pressure and Pump Performance
As the head pressure increases the gph will decrease. Use the following guide to determine the amount of head pressure in your application in order to determine how much flow you will get from any pump.
- Each 90-degree bend in the plumbing will add about one foot of head due to friction. Each 45-degree bend will add 1/2 foot head pressure. This includes any bends in filters, chillers and uv sterilizers.
- As a result of friction, each 10-foot horizontal run of pipe will add a foot of head pressure.
- In an open system (a system using a sump), each foot of vertical distance from the intake of the pump to the return into the aquarium will add one foot of head pressure. The vertical distance in a closed system does not affect head pressure. A closed system is one where the pump draws water directly from the aquarium and returns water directly to the aquarium.
Note: We have not included any info for how much head pressure there is when you restrict the flow by using hose or return fittings with a smaller diameter than the pump outlet. This depends on the size of the pump outlet and the amount of restriction. In general, it increases head pressure a great deal and is not advisable.
Aquarium Water Pump Redundancy
You'll be better off with two or more smaller pumps than one large pump. Having at least some water turnover is critical to the survival of any aquarium, and if you have more than one pump when a pump fails you will not need to desperately locate a replacement pump. An aquarium can completely crash within eight hours if there is no water turnover because pumps are critical to aeration. An air pump will keep an aquarium aerated--you may want to have a battery operated air pump on hand to keep your aquarium operational during power outages.