As you are finding out, there is more to a bottom diffusion aeration system than just putting something in the pond to make bubbles come up to the surface.

Can you answer the following questions?

How many gallons of water does each diffuser bring up to the surface of the pond per hour of run time? That number will change according to the depth that it is placed.

How many CFM does your compressor put out at 6 psi backpressure?

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).