This water conditioner is by far the very best that I've ever used. It does a great job on new or existing aquariums. Because of the high price, I was a little skeptical at first, but if you figure that you only need one cap full instead of several ounces of the other brands, it is actually cheaper per application that the others.
I highly recommend it.
Prosworks well; good price per application; buying it from Pet Guys, they are fantastic!
ConsIt smells terrible but the fish don't seem to mind.