I would think it would create a vacuum effect and draw the water up from lower... again just thinking
I believe that you are correct. I don't see how it could work any other way.
The bubbles go up, and bring water with them. When it gets to the surface the only place left to go is outward from the bubble column.
So you get a vortex effect around the diffuser, but vertical rather than horizontal like is seen in a whirlpool or river eddy. Everything in
the water such as weed growth, rock piles, brush, dock posts/floats, etc., will have some effect on the distribution of those currents.
Bottom contour will also have a great effect - dropoffs, humps, ridges, etc. If the pond is anything other than a round bowl with a
smooth bottom, and a single diffuser set dead center, there must be areas that receive a greater degree of mixing compared to other areas.
I set the diffuser in my pond 4' off the bottom with the intention of leaving some undisturbed water for a cool water refuge area.
Is 4' enough? I'm not sure. The thermometer I bought only has a 10' cord. Right now my pond is 83.5° at 6", and 82.4° at 10'.
I really need a longer cord to gather meaningful data. Anecdotally, we are able to feel noticeably cooler pockets of water when
we go swimming.
We've all read Cody's comments relating to temp/DO preferences. Those among us who are anglers know that it's quite common
to catch fish below the thermocline during the hot part of the year. Do they stay there all the time? Obviously not, but it's apparent
that they spend time there. Do they go there just to feed, or do they go there to cool off, and maybe get a snack if the opportunity
presents? Who knows?
I think snrub called it when he said aeration is an art, rather than a science.
