I used Schultz Aquatic Plant Soil in one of my most recent tanks. It was REALLY dusty when I opened it -- to the point that I was hacking and coughing. I rinsed, but should have rinsed better, because it clouded my tank for quite a while.
Additionally, I would recommend adding some a layer of peat, or perhaps mulm from an existing tank, when you add the substrate. I tried to start my Schultz tank with root feeders, and they really struggled for the first two or three months. Ever since the tank has built up its own layer of mulm, however, the Schultz has been growing the plants really well.