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.