Yeah we need someone with 2 identical ponds with a depth of atleast 10 ft.

Cecil I think buckets of dyed water would get alot warmer than clear water, probably too small for testing the affects on deeper water.
Before I increased the inflow to my pond the tannin water would only have a summer visibility of about 2 ft and even though the pond is only 8 ft. deep there would be quite a difference between surface water and bottom water, but then I had the variable of 35 gpm gravity flow from the stream so that could have made the difference rather than brown water restricting sun light.
Bill, I see you've posted while I was doing my slow typing, looks like you've added more "It all depends".