Selecting the correct pump is essential, whether you choose to power a waterfall or simply circulate water through your filter. Most beginning pond-keepers buy pumps for filtration. When choosing a pump for filtration, the gph (gallons per hour) of the pump is the most important consideration. In addition, the type of pond you have will determine what power your pump will need.
How big is your pond?
When you know the volume of water in your pond, you know how many gallons per hour a pump must be
able to handle in order to move the water to provide sufficient circulation. This includes components that affect the volume of the water. As a general rule, circulate pond water a minimum of once every hour. Insufficient circulation can cause areas of stagnant water, low oxygen levels, and many other problems, which eventually lead to an unhealthy pond.
How far do you need the pump to push the water?
To determine the appropriate pump for your particular pond, there are several factors to consider. For example: Are you moving up an incline, through a filtration pump, or other equipment; how far are you pumping the water; how much tubing are you using; and how many elbows, bends, and other plumbing fittings do you need? Such factors will influence the maximum head height required for your system.
How much energy are you using? If you are concerned about energy usage, as most of us are, choose the pump with the lowest wattage that will fit your needs.
What other equipment are you using?
Consider what other equipment you may be using and look at additional fittings you might need for tubing and other plumbing supplies. Pipe thread fittings come in MPT (male), FPT (female), or barbed (fit into female fittings to convert them into male fittings).
Pumps run 24 hours a day and are the chief piece of equipment responsible for keeping your pond healthy. Read product descriptions carefully to make sure you are making the correct pump choice.