In a nutshell... multiply you pond's length, width, depth, and 7.5 to get how many gallons your pond holds. After this simply get a pump that pushes more gallons per hour (GPH) than the gallons your pond holds. Water in your pond should circulate no less than once every hour. This video goes over two different pumps that I have used (one kind broke 2 times), why I had to chop my pond into sections when measuring the pond's length, width, and dept, and what causes your pump to push less water per hour than what the pump is supposed to push. Keep in mind that this is simply a hobby of mine and you should always do additional research so you can make your own informed decision on what you want to do. Thanks everyone :) This is the link/URL to the pump I bought from The Home Depot. https://www.homedepot.com/p/TOTALPOND... This is the link/URL to the pump I bought from Harbor Freight. https://www.harborfreight.com/2500-gp...