The PoolRx+ booster contains the additional minerals needed to replace minerals that are lost through back wash, splash out and algae kill. PoolRx+ booster can also be used for larger pools that need additional minerals when initially installing a PoolRx unit. These minerals do not need to go back into the PoolRx unit; they just need to dissolve back into the pool water. These minerals generally need to be replaces every 4 – 6 months, depending on your swim conditions.