Rebecca, Figuring 7.5 gallons per cubic foot your
14x20x2 feet equals 560 cubic feet which equals 4200 gallons. And if you think for one second I did the math on this you are soooooooo wrong. I haven't a clue. DH did it for me. BTW, the accu-clear works best on coagulating dead algae so that the filters can pick it up. It does not work well on blooming algae. For a pond that size you need at least a 40 watt uv light and a minimum of 1800 gallon per hour pump. DH said if you would like to call he would be happy to talk with you. Email me for phone number if you want it. Good Luck!