PoolRX 101067 4-Pack Black Unit Algaecide for 20000 to 30000 GallonsThe PoolRX 101067 4-Pack Black Unit Algaecide for 20000 to 30000 Gallons is part of the PoolRX products which is developed to be a unique chelated mineral algaecide and chemical reducer that is effective for up to 6 months. It is the recommended algaecide solution for all chlorine pools, salt pools and spas which is suitable for Residential and Commercial use. It can be placed in a pump basket or skimmer where its minerals can function immediately and eliminates all types of algae so you can have an improvement in your salt or regular pool swimming experience. This product provides a 50 percent reduction in your chlorine or salt chlorine demand and a 100 percent elimination of the need for harsh chemicals like phosphate removers, clarifiers, sodium bromide, and other chemicals. It can also descale the salt cell in your chlorinators which is equal to prolonging the life of the cell. PoolRX is very ideal to use with Chlorine, Salt, UV or Ozone systems. This particular product, PoolRX 101067 4-Pack Black Unit, consists of 4 Units of PoolRX 101066 Black Unit and intended for a Pool Size with 20,000 to 30,000 Total Gallons and can also be recommended for 40,000 to 50,000 Total Gallons. Since this has already 4 units of PoolRX Black Unit, it is also ideal for 60,000 to 80,000 Total Gallons using 2 Units of PoolRX Black Unit. For 90,000 to 140,000 Total Gallons, you can use 3 Units of PoolRX Black Unit. You can replace PoolRX in the basket every 12 months. Please note that PoolRX is not compatible for use with bromine or biguanides.