No matter what size of a pond you have getting the right size pond pump is critical. When you are looking for a water pump for your pond. The bare minimum you will want to use is a flow rate of half of your pond size in gallons per hour. So if you have a pond that is 300 gallons you would want a minimum of 150 gallons per hour for your water pump. Keep in mind this is just a starting point. When adding a water fall or you need to increase the size of the pump by 150 gallons for every 10 inches in height of your waterfall. If you are going to add fish to your pond then the water flow needs to really eaqual however, many gallons your pond is. So if you have a 300 gallon pond then you need a pump capable of producing 300 gallon per hour in the flow rate.
Adding a submersible water pump is often the first choice of people who are building a pond or water feature for thier yard. There are a couple of reasons for this actually.
The lifespan of any water pump though has a lot to do with a few factors, from how clean your water is, how often you clean your pump and how often you run your pump.
Typically an external pump is very efficient when it comes to the amount of energy they use. They also tend to last longer as they are not being subjected to being in the water all the time. Really the biggest downfalls of a external pond pump is it will require extra plumbing along with finding a creative way to hide the pump.
To be able to estimate how much energy your new system is going to use you can use this formula: amps x volts divided by 1000 x KWH cost x 24 hours-a-day x 30.4 days-per-month = cost per month.
If the pump is rated in watts instead of amps use this formula: watts divided by 1000 x kWh x 24 hours-a-day x 30.4 days-per-month.
KWH is the kilowatt-hour cost, which you can get from an electric bill or by calling your local electric company.