We have a 10 A. quarry that has 8 A. that is 20 to 35 ft. deep. It is completely spring fed and with berms all around there is no runoff that can get in. We have had it for three years now. Our PH is 8.0 and we had to add quite a little structure. There is no electricity so no aeration. We have found that year round we have fish at all depths from top to bottom. We have a very good depth finder to find the fish. I am always surprised how many LMB, BG and other fish we catch right off the bottom. I would not discount the value of the deeper water.