When deciding which pump will work best for you pond, you will need to take three things into account: pond type, head height, and friction loss.
Pond Type:
Water Garden, Few Small Goldfish: Circulate total pond water volume every 2 hours. Example: 2,000 GPH pump for 3000-gallon pond with 2" waterfall.
Fish Pond, Several Small Fish: Circulate total pond water volume every 1 hour. Example: 3,800 GPH pump for 3000-gallon pond with 2" waterfall.
Koi Pond, Several Large Fish: Circulate total pond water volume every 3/4 of an hour. Example: 5,500 GPH pump for 3000-gallon pond with 2" waterfall.
Head Height:
To calculate the head height, take the vertical height of your waterfall; the distance between where your pump is (typically in the skimmer) and where your waterfall is, and adding the static head pressure (pipe and fittings) 1′ for every 10" of tubing and 1′ for every elbow or "T" fitting.
Example: 3′ (vertical height) + 2.5 (25′ of tubing) + 2′ (for 2 elbows) = 7.5′ of Dynamic Head Pressure
Note: Head height is important to take into consideration due to the laws of fluid dynamics. Please refer to the flow chart above to help choose the correct pump.

CHOOSING THE RIGHT SIZE TUBING FOR MY WATER FEATURE

When Sizing your Freeze Flex Pond Hose, make sure you choose a pipe that will not restrict the flow of your pump! If your hose is 1.5" and you buy a 6,000 GPH pump, your pipe will only allow 4,400 GPH to pass through it. You will be wasting money on electricity and paying for a stronger pump that will not give you the desired result. You will need to run an additional pipe or change your hose to get the desired flow rate! Many people expect to achieve greater flow by simply buying a larger pump. They do not realize that flow will not increase unless the tubing can also support this increase inflow. Please do not let this happen to you. Using the chart above, you will be able to easily determine the best size tubing for your pump size. Do not use pumps on an extension cord. They must be run on a dedicated 15 Amp GFI circuit.

Rectangular Ponds
Length x Width x Average Depth x 7.48 = Gallons
Example: A rectangular pond that is 15’ long, 10’ wide and 1.5’ deep is… 15’ x 10’ x 1.5’ x 7.48 = 1683 Gallons
Oval Ponds
Length x Width x Average Depth x 0.8 x 7.48 = Gallons
Example: An oval pond that is 15′ long, 10′ wide, and 1.5′ deep is… 15′ x 10′ x 1.5′ x .08 x 7.48 = 1346 Gallons
Round Ponds
Radius x Radius x Average Depth x 3.14 x 7.48 =Gallons
Example: A round pond that has a 12′ diameter and is 1.5′ deep is… 6′ x 6′ x 3.14 x 1.5′ x 7.48 = 1268 Gallons
Streams
Length x Width x 0.25 x 7.48 =Gallons
Example: A stream that is 20′ long, 3′ wide, and 3" deep is… 20′ x 3′ x 0.25 x 7.48 = 112 Gallons