Hi zap- I'm located in NE Ohio and have a small, 1/4 surface acre pond with White Spruce, White Pine, Pin Oak, native Willow, Maple and even Bald Cypress within 20' (or less) of the pond. I've had leaves enter the pond for quite a few years and while I occasionally see a small fish kill- maybe 3 or 4 fish total per season- I doubt that it's related to the Oak leaves. I've definitely seen the tannin staining the water that you refer to. I think the bigger concern would be the accumulation of organic material (leaves) on the pond bottom and the resultant muck it creates. The muck removes dissolved oxygen from the water, can produce hydrogen sulfide gas, and both conditions are of course bad. (There was one benefit of starting aeration and releasing the hydrogen sulfide gas from the accumulated muck-- it led to the demise of a few muskrats! But I also unknowingly placed the fish at risk in the process due to inexperience and knowledge of proper aeration startup- another subject...should have read more in the PBF before starting aeration!! LOL!)

I've become more concerned with eliminating muck in our pond so I've added pond aeration and I intend to remove a Maple, white pine and a willow that are the biggest contributors of leaves to the pond at present. I would rather not remove the pin oak that drops a lot of leaves now that it's 50' tall. So the jury is still out on the Pin Oak. I don't know about your experience with wind, but over the last 15 years I've noticed a significant change in the frequency of wind direction from primarily W/SW to a more prevalent E/SE. In my case this aggravates the leaf introduction to the pond due to the trees' locations. Just keep in mind the leaves once in the pond will become muck and will accumulate year after year. So you will have to choose what you value more-- or determine a tradeoff. Welcome to PBF BTW!