In addition to the previous words of advice, you may want to look into reasons for algae to have developed (Dubby was alluding to this I believe).
Prevention in this case (as in most cases) is much easier than the cure. In my case, direct sunlight was (and still is) the culprit in my hair algae problem. You might also want to read about phosphates and nitrates, and see if they are present in your tapwater. HTH~