So many backyard pond pumps to choose from: Which one is best for me?
Backyard Pond pumps do one thing: They move the water in your pond from where it is to somewhere else. Most of the time they pump it up and over a waterfall. Other times they pump water through a spitter, an ornament in or next to your pond, often a frog, dolphin, fish or piece of statuary. Sometimes they pump water up in the air like you see in huge commercial ponds near the mall or on the farm.
There are things you must know before choosing the right pump for your pond. Half of your pond water has to move through your pump every hour. So if your pond is 1000 gallons, your pump has to pump 500 gallons per hour or GPH. As this is a bare minimum requirement, you would be best to consider a larger pump. For example, if you are moving water over a wide or tall waterfall, you need more GPH. If you are pulling water through a filter, you must be sure you are pulling enough to make the filter work properly. So figure on buying a larger pump than the minimum size, so you have some wiggle room.
So now you have water moving around in your pond. It sure looks nice and sounds great going over that waterfall, but moving does more then just look nice. If you have fish in your pond and feed them, the pond will be out of balance ecologically. Feeding fish makes them grow too big for the available oxygen, so your water needs to have oxygen introduced. Your pump does that. If the pond water surface is moving oxygen is being absorbed by the pond water and then your fish can breathe easily.
If you do have fish, and most pond owners do, you probably have a filtration system. The pump also pulls water through that filter system, either mechanical or biological. That filter pulls suspended debris out of the water. Usually the debris is algae and when you get too much algae, your water will turn green. The proper filter can keep that from happening. So the pump must be big enough to meet the needs of your filter.
You have three choices of pump types: Submersible, external and solar. Submersible pumps cost less, but do not last as long. They are still the pump of choice with most pond owners. Because they are made of a resin material, they can be used underwater, but if the seal is broken, the pump must be thrown away. It cannot be fixed and returned to the pond safely. A submersible pump can easily last 5+ years if cleaned regularly. Cleaning is important to a pump's life. They often sit on the bottom of the pond and suck in all the rotted organic debris sitting in the bottom of your pond. If left uncleaned for any length of time, the pump impeller, a reverse propeller that sucks water in, can become damaged quickly.
In general, the more expensive the pump, the longer it lasts. Always check the warranty length of any pump.
External pumps last longer, pump more water, can be repaired and are more expensive. They also need to be hidden somehow. No one likes to look at a pump and filter set up right next to their waterfall. But if you have a large pond, you might be better served by a external pump. They are certainly more efficient than submersible ones, they cost less to operate and can pump more water. Because they are stronger, they can work with most biofilters and last longer because they do not have to work as hard. If I were to get an external pump, I would look for one that pumped as many gallons per hour as my pond held. If I had a 5000 gallon pond, I would want a 5000 gph external pump.
Solar pumps are starting to come into their own. We still have a long ways to go before they will perform as well as we want them to, but the technology is coming along. The biggest drawback of solar pumps is they will not pump if the sun is not shining, so your pump will be off during gray days and at night. As solar energy storage technology becomes more widely available, solar pumps will become the best buy.