Natural Chemistry Pro Series Dual-Action AlgaecideThe Natural Chemistry Pro Series Dual Action Algaecide is a fast acting algae remover that is highly effective. This liquid formula will kill all forms of algae including green, black, and mustard algae. It is formulated to be compatible with most pool sanitizers. See results in your pool with no foaming in just 24 hours, and it can be applied to pools with connected spas or jetted returns.