Bio-Chem Zorb?

[foodandfish]

I justt had a quick question about Bio-Chem Zorb that comes with the Rena Filstar xp series. I noticied that while im washing out the dust, the water never seems to run clear but just black. Even though the direction says that its shouldnt run clear, im worried that it will dirty my tank. What are your experiences with this product? Thanks