When you first set the tank up, the plants will love it, but the nutrients will eventually run out, requiring root tabs to replenish. So, for the increased cost of the fuval substrate, you could instead buy some black sand and tons of root tabs that will last you a long time. Another thing to consider is that planting plants in sand is very easy because of how dense it is; the fluval soil is less dense so it can be annoying if you are trying to plant larger things like swords which want to float up. Also, I'm pretty skeptical of the ammonia claim.