As Eric noted, you probably have some large bluegill in the pond; a pond overcrowded with bass is the ideal scenario for growing trophy bluegill (when coupled with a good food source for the bluegill either through fertilization or supplemental feeding or both). A couple good places to try fishing for the bigger bluegill would be 1)any flats between two and six feet deep close to deeper water, and 2) the dam of the pond if it has one. Additionally, if there's a bank of the pond that is more overgrown than the others either with grass or trees or both, that could be good due to insects etc. falling into the water. Try using light line, six-pound-test or smaller, with a very small hook (#8 or #10), little or ideally no weight, and the tiniest balsa float you can find set to keep the bait just off the bottom. The bigger bluegill aren't going to hang in a few inches of water like the little ones do. And if your water is clear enough that you can look for fish, the bigger 'gills could be in eight or ten feet of water if not deeper now that the turnover has occurred.
Is your primary goal for the pond big bass or big bluegill? If it's big bass, you'll definitely need to harvest several of those smaller bass, probably at least thirty per acre, before you start seeing significant growth in the bass. If on the other hand your goal is big bluegill, don't harvest any of the bass, install two or three automatic feeders and start feeding two or three times a day with a good quality food like Aquamax, and start a fertilization program next spring.
Cover lessens the ability of the bass to control the bluegill. More cover will help, though, if bass are your priority, because it will allow more bluegill to survive, which in turn gives the bass more forage. If bluegill are the priority, you wouldn't want to add a whole bunch of cover because it could allow the bluegill to increase to the point that their growth slows; but some cover could be good just to concentrate the bluegill and make them easier to locate and thus catch.
