Whether you have a preformed or a liner pond, a pond pump is a paramount component of any water feature.
Pond Pumps are available in both submersible and external ( out-of-pond ) models. For the smaller pond (up to 1000 gallons of water), a submersible pump is the more economical and practical option.
A Submersible pond pump can be placed directly in the fish pond and require relatively little installation. They are free of distracting noise, and for smaller ponds, can easily be utilized to drain your pond (if you hook up a hose to the output flow of the pump ).
The pump is sized by gallons per hour (GPH) output at one foot of lift or height. It is recommended that you circulate your body of water at least once every 2 hours. Therefore you will need to size your pump to ensure that it has half the GPH rating as the volume of your pond in gallons.
For example, if you have a 1000 gallon water feature, you will require at least a 500 GPH pump.