After thinking about your question for a while thought I would share what I know which is not much. The guys that fish a lot and the experts will have a much better handle on which fish use which depths and how likely they will use your deeper water.

But I have went scuba diving a few times in my pond in the summer. My observations are these.

If you have a good algae bloom (say 2' for example which is about where mine is right now) or otherwise have turbid water, it gets dark very quick as you decend to depth. I was snorkeling the other day and dove down to see how clean the diffusers were. It was pitch black at 8-9'. That tells me it is unlikely that any sight feeding fish are going to be cruising at that depth for feeding at least. Maybe they go down there to rest, I simply do not know. Catfish that feed more by smell I would think would be more inclined to go down there if there was any food.

In the fall it gets clearer in my pond and I can see the diffusers and bubbles at that depth. It is kind of like twilight and pretty dark, but with my face a foot from the diffusers I can see them operating. I will say that last fall when I pulled the diffusers I pulled up bullfrog tadpoles that were under the diffuser disks lodged in between the disks and housing. Also this spring when I unscrewed the disks I found a dead dried up minnow making me think the minnow was using the diffuser as a refuge. So at least minnows and tadpoles were utilizing the 9' depth in late fall.

I know fish use the deeper depths in lakes that are more clear. Just not sure about ponds that often are not as clear.

John

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