Hasa Algi-Control For Yellow/Green Algae Treatment 1 Gallon P/N: 72041 HASA Algi-Control is efficient, economical and stable when used in proper dilution. Algi-Control is compatible with most chemicals used in pool water and will not damage tile, concrete, metal, or plastics. Algi-Control keeps pool water sparkling, clear, and free of visible green and blue-green algae, slime and green brown colors. Algi-Control improves filter operation and cuts down the need for other chemicals. HASA Algi-Control gives tone and a pleasant feel to swimming pool water.