Half Off Ponds PARP-60KDD2 3.9 CFM Aeration System w/ 2 Double-10 EPDM Diffuser. Manufacturer Warranty 2-Year Manufacturer's Warranty. Length x Width x Average Depth x 0.25 x 7.48 = GALLONS =Gallons Example 15' long, 10' wide and 1.5' Deep Pond 15' x 10' x 1.5' x 7.48 = 1683 Gallons.