Hi Chris -
Generally, the deeper the diffuser the more water is pushed toward the surface because as the bubbles rise they spread out and influence more water. In shallower water there is a much shorter distance for the bubbles to spread out, so your gallons per minute of water moved to the surface decreases. You would need less diffusers in deeper water and more in shallower water to get the same turn over rate. I know that our diffusers become inefficient in depths under 4 feet. As for a maximum depth, the limiting factor is usually the psi limit of the compressor. You can go 30 + depth if you have the right compressor.
You usually want to place the diffusers in the deepest most central locations spread out depending on how many you need.
There are certain instances when you don't want to put them in the deepest area of the pond for example if you have coldwater fish species or for winter aeration.
Your best bet is to contact an aeration specialist and explain your goals and give them the details of your individual pond. They can then make an educated recomendation of what system you need and where you should locate your diffusers. Aeration, if done correctly, is beneficial for any pond.


Sue Cruz
Vertex Water Features
www.vertexwaterfeatures.com