This is just a guess on my part. Someone else may come along with actual experience. But this is the way I vision it.

The pipe should work as a "chimney" and draw water from the bottom as you describe as long as you place the diffuser in the upper part of the pipe with some space around the edge of the diffuser to allow water flow.

You can't get something for nothing so water flow will be reduced compared to the diffuser placed at full depth. Water movement is caused by the bubbles rising and the deeper the diffuser the greater expansion of the bubbles so the more water pushed. So you obviously would be better off with diffusers deeper but I believe the chimney would draw at least some water from deep.

No experience here. Just as I see it in my minds eye. Take that in consideration.

John

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