sounds good but I cant see how this would work long term! It would be good to have heard a few reviews from people who have used it long term as to how good it was. Also it says that you wait a week or something and then add the fish - no cycling the tank to get the bacteria built up??
I wouldnt try it myself, unless it was in a small tank as a try out. I quite like having control over what goes on n the tank - and it makes you keep an eye on the fish too and check their health too.
be interesting to hear how you get on with it if you decide to give it a go, but I wouldnt use it.