Soilmaster is actually used for drying baseball fields (like turface). The key to a good aquatic substrate is a high cec (cation exchange capacity) and contains iron. Most substrates designed for planted tanks are calcified clay which contains iron. Cation exchange capacity is the ability of a substance to draw in excess nutrients to reach equillibrium and then leach them back out when equillibrium is not reached. (For example, draw in excess No3 when the water column is abundant and release it when the water column is depleated).