I'm in Northeast PA and have never used an algecide. I keep the equipment going as long as possible, usually mid November before I blow the buried pipes, so I can circulate a little every few days and keep the chemistry right. I also open early and the only time I get an algae problem in the Spring is when I get lazy and cheap so I don't circulate as much and the water warms a little. I'll see it and get right on it.
Al