Yup, I had some bouts with this weird nasty slime on my roots, like glue almost, started off white then turned brown. I started treating all my water with a UV light before introducing it to the plants, I actually use one from petsmart. :)
I also hit the water with h202 when I fill up my plain water res, just as a little extra safety precaution.
After a couple days of the water circulating through the UV, the h202 has dissipated(I use a much larger dose than if you were dosing a system with plants in it).
I tried just hitting the res with h202 alone but I still kept getting slimed
Personally I think the UV sterilizer is one of my most important pieces of equipment, haven't had the slime problem in several years now. :)