If your MD3 is an Easy Pro model it is 1-3 cfm rated. You can rob some cfm from them "but"that is a med to large slit and not a good choice for shallow water in the other pond. Look at the Vertex Shallow Water model as it will only require 1 cfm and will give you 2300 gpm lift at 8 ft thus leaving your other two discs within the suggested rate range.This diffuser will operate to depths as low as 4 ft.When you tap into the air supply use at least a 3/4 to 1 inch line to the pond edge and then .58 to .625 weighted line from there to accomodate the vane pump.You want to lessen the friction loss and back pressure as much as possible on a vane pump