You may want to consider nonflying ducks. I have a 2 acre pond that does experience complete water turnover several times a year which makes chemical solutions too expensive. I introduced Rouens and Black Swedish ducks and they have solved my algae problem as well as controlling duckweed and all the other weeds in the pond and snails. Of course you don't want too many ducks because they will cause several other problems for you. 5 or 6 to start with should give you an indication if you have enough for a 1 acre pond. As for timing, it took them until late summer to catch up in my pond (15 acre ft) and I am guessing that they will stay ahead of the curve this year. One other point, we have lots of wild critters out here and I had to build a raft to provide night sanctuary for them - coyotes, coons and bobcats love duck!