Hey northernbudmen...hello to a fellow "Great White Northern"...I have had the problem that you speak of...The Slim. What are your water temps? My slim came to me when my water temp went to high. Try to change your water and lower the temp. You can freeze 2 liter bottles of h2o and drop them in your res or bucket to lower the temp. Also I have heard of people using hydrogen proxide to combat this problem. I use Hyrdozyme and have not tried HP for this problem. The Hyrdozyme works great at keeping the roots clean and white. Hope this helps.