Back Up 2 is a non-staining formula that prevents a wide variety of algae. There are a lot of different types of algae that can grow in lots of places in your pool. Bioguard products have been tested and proven to be effective. Add BackUp2 to your list if your regular maintenance isn’t enough to keep algae from growing in your pool. BackUp2 is a powerful wetting agent and surfactant that helps to work into those hard to reach cracks and crevices. This product can be used weekly to prevent algae. This product is not appropriate for pools with attaches spas or water features.