Pre-Vent is a unique formula which seeks to succeed where many commercial bacteria cultures fail.Pre-Vent is safe for all pond fish, plants and biological filtration systems.Pre-Vent is to be used every 10-14 days approx. to help rebalance your pond. To aid in the prevention of the return of stubborn Blanketweed.To be used as a follow-up to the Number 1 selling pond product: Cloverleaf Blanket Answer.Pre-Vent is a unique formula which seeks to succeed where many commercial bacteria cultures fail. Pre-Vent is safe for all pond fish, plants and biological filtration systems. Pre-Vent is to be used every 10-14 days approx. to help rebalance your pond. To aid in the prevention of the return of stubborn Blanketweed. To be used as a follow-up to the Number 1 selling pond product: Cloverleaf Blanket Answer. We strongly recommend the use of Cloverleaf Absolute Pond Pearls for the general wellbeing and maintenance of your pond. Its unique natural bacteria will consume and break down organic waste material that accumulates in your pond and filter, converting it to nutrients for pond plants.