Next spring I plan to drain/refill my AGPool (various reasons). I think I have algae in my pool b/c I have a brown substance that settles on the bottom yet clouds up when it gets stirred around. My question is since I plan to drain/refill the pool in the spring can I just close my pool even though I suspect algae? Do I have to add any "winterizing" chemicals since I will be draining the water next spring?