Theoretically, the hairgrass with hold the particles of Aquasoil down and together, and keep it from getting stirred up and into the water column. I have Aquasoil in my own tank, and I never, never, never vaccuum, and I tried not to disturb it at all really, because of the cloudiness it produces. Make sure you plant the hairgrass with tweezers, btw, in order to keep disturbance to a minimum.
It could be that you do have defective AS. Take a piece out and crush it with your fingers. If it turns to mud without much pressure, it's defective or its taken too much of a beating from being moved around too much. If it's still pretty firm, its probably normal.
I'm also very careful when refilling my tank... pain-stakingly so. I allow no direct flow onto the AS, since it's so light, and in order to maintain clarity.
