if it is organic i have heard it is the right stuff. mine has been running for about 2 weeks and i poke the gasses out everyday and so far everything seams good and the plants are growing like crazy!
i put approx 1 inch of soil and capped with 1 to 1.5 inches of gravel on the top. after a week of running i started poking the gas bubbles out of the dirt. So far no deaths in tank. all plants are growing awesome and not a spec of algae .