Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Mineralized Top Soil is a DIY material.
Start with a soil that is more sand, silt and clay (not very much clay) and a little organic matter (not very much). Help it to age by alternately wetting and drying it.
Topping material is your choice. It serves several purposes. With a fine material it reduces the amount of clouding. It can be cosmetic, it may hold the plants into the substrate a bit better. With EC, I find topping is optional. EC looks good, is heavy enough to hold the plants, and does not cloud the water.
If the substrate is a very lightweight material, then any topping might sink through it, so lose any benefit of being on the top. (ie: Soil Master Select is so lightweight that gravel and sand ends up at the bottom rather quickly)
An alternate is to use some of the minerals that become fertilizers at the bottom of the tank and use EC, ADA products, or other substrate.