Find Pond Filters

In order to keep your pond clean, you need the proper size filter. Follow these instructions to find the filter size you need for your pond.

You first need to figure the volume of the pond. The formula for this is:
Average Length (feet) x Average Width (feet) x Average Depth (feet) = feet³ THEN
feet³ x 6.23 = volume in gallons

You will need to make adjustments to the pond volume if you are dealing with a very shallow pond or if it is in full sunlight. If your pond has an average depth of 2 feet or less OR if it is in full sunlight, you need to add 25% to the pond volume. The formula is:

Pond volume in gallons x 1.25 = pond volume for filter shopping purposes

If your pond has an average depth of 2 feet or less AND is in direct sunlight, add 50% to the pond volume. The formula for this is:

Pond volume in gallons x 1.50 = pond volume for filter shopping purposes

Now that you have the volume of your pond figured out, you need to figure your pond filter size. The entire volume of your pond should pass through the filter at least once every three hours. If you are looking for a very clear pond, the entire pond should pass through once every two hours. The formula for this calculation is:

Volume / 3 (maximum hours for full pond filtration) = GPH (gallons per hour) filter size you need. This is the MINIMUM filter size you need.

Volume / 2 (number of hours for a very clear pond) = GPH filter size for a clear pond. This is the MAXIMUM filter size you need.

Because pond filters come in standard sizes, you might have to find a filter that is somewhere between the minimum and maximum filter size you figured.

EXAMPLE
Volume 6 feet long x 4 feet wide x 3 feet deep = 72 THEN 72 x 6.23 = 449 gallons
Pond in full sunlight 449 gallons x 1.25 = 561 gallons
Filter size MINIMUM 561 / 3 = 187 GPH
Filter size MAXIMUM 561 / 2 = 281 GPH

The acceptable filter size for this pond is between 187 and 281 gallons per hour.