A person just getting into ponds may be confused by the terminology and types of pond pumps, particularly when trying to determine the type of pond pump they need. The most common question is “What is the difference between an external pond pump and a submersible pond pump?”
The easiest and most simplified answer is to say that one is used outside of the pond (external) and a submersible pond pump is used inside the pond (submersible). However this really does not fully answer the question.
It is true that an external pond pump is placed on dry ground outside of the pond, but there are other things to note about an external pump. External pond pumps. are going to be best for larger ponds due to the fact that they are more energy efficient and are capable of moving larger volumes of water. Usually ponds over a couple of thousands of gallons will benefit more from an external pump or ponds with larger water features may also need a larger external pump due to the distance that the water is going to travel to supply water to the water feature as in the case of a large waterfall. It is also important to note that some external pumps may also need to be hardwired and are not simply “plug and play” like the submersible units.
Speaking of submersible pond pumps. Submersible pond pumps are going to be best used in small ponds or when powering smaller water features or equipment like a small filter. Submersible pond pumps are very easy to install. Basically they are placed in a desired location in the pond and plugged in and that is it. Furthermore, many submersible pumps come with fountain and spray attachments so that they can easily be utilized as a small fountain feature.
Remember to effectively choose the correct pond pump for your pond, pay attention to gallons per hour (gph) that the pump moves and select the pump that will move the entire volume of water at least once per hour. So a 5000 gallon pond will most likely need an external pond pump with a rated GPH of at least 5000.