I'm on edge about getting one! I also have read about them and don't know if it will help. Most people using them, say it's a good way to prevent ich and control algae and also clears up water!
My water is clear even though I have to clean the glass almost everyday from green algae growing. I do however have a hippo tang that has started to show signs of ich.
I don't have a QT set up so I can't separate him! I am treating him with an ich medication that won't harm the rest of the tank. He is eating well so I guess we'll see.