BioGuard Banish kills ALL types of swimming pool algae. This fast-acting formula will produce results in just 24 hours. This product allows swimmers to return soon after treatment. It is formulated to clear up swimming pool water and kill algae. Approved for use in chlorine and bromine pools. Banish does not affect pH levels, so no readjusting is necessary after application. This product is also approved for use during shock treatments, so there are fewer steps than when using other copper-based algaecides.