Product review (4 stars): Doing a great job, just add after you fill the tank.
So far so good. I was using grapefruit seed oil as a natural alternative, but it wasn't doing the trick unfortunately. So, I decided to try this in my Evap3 humidifier. A week later and it really seems to be doing a good job at eliminating buildup and mold growth, which I felt like was almost an every day issue before I bought this. My only gripe is I wish they'd let you know to add after the water is filled in your tank, otherwise it foams like crazy. Directions just say to add 1 capful per gallon, so it would be helpful. I add at the end, cover and give a few shakes and it works fine. Foam goes away very quickly.