Bob, if my memory serves me, I think I have read that a pond should have about 20% structure as a rule of thumb. However, I have a hard time defining that. Is it 20% of the shoreline area or the bottom surface or the volume? Hopefully you'll get the attention of someone in the know soon. I have used about 15% of the shoreline from the 2 foot depth to the 6 foot depths of my 10 foot deep pond.

And as far as oaks go, I know I have read that there have been some problems with green oaks going in the ponds before they dried.

Here's a good read on the topic of root wads and trees as structure...

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=434384

I have used Osage Orange wads with no noticeable effect on the FHMs stocked this spring. My water is a little tea colored, but I don't think it is from my root wads alone.

Fish on!,
Noel