Soilmaster, filter sand, Flourite, etc. are all inert substrates. Soilmaster, like Flourite, is a baked clay product, and it provides good cation exchange capacity. You have to fertilize with all of these products. You can do water column fertilizing and/or substrate fertilizing, but you have to provide the fertilizers. Even ADA Aquasoil only contains enough fertilizers for a limited amount of time. Once those are used up you still need to provide fertilizers.