I had root problems in the beginning too. I did cure the root rot with physan 20 I believe it is called? I then discovered and used Zone for the rest of that grow. I ended up harvesting early, but I did save the plant. Since then, I have used The Gold Range Zone, and Even at the end of my grows, there is not a slick spot to be found in my res. It is as clean as the first day I filled it, with the exception of any gunk from the rocks.
Haha I actually used DM zone that whole grow and my problems still happened! I was pretty disappointed! I still have the bottle, haven't used it since as my first dwc grow was a year ago. I'm actually currently on my 2nd dwc grow and this time I'm trying bennies instead of sterile. It actually was something I had a hard time making a decision on lol. I figured if anything went wrong I could always use the zone to try and kill everything to fix it. ;D