This stuff is awesome. It is essentially Hydrogen peroxide, but way stronger. A very small amount and it will prevent algae. Before I started using it I had to constantly clean out all my lines or they would clog. When cleaning a good amount of black slime would come out. Now I can do a full run and not have any build up. You have to be very careful when using this stuff. It will pretty much bleach anything it comes in contact with, and WILL BURN YOUR SKIN.