What size filter do I need for my pond?

What size filter do I need for my pond?

The rule of thumb is that you should have a filter that is rated for about 1.5 times the number of gallons in your pond. So if you calculated your pond contains 400 gallons, 1.5 x 400 would mean a filter rated at 600 gallons per hour (gph). All pond filters will have a flow rate measured in gph.