Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
When it first came out Soil Master Select (Charcoal) was on the market and the 2 materials looked exactly alike.
They are a montmorillonite clay, baked until it is a certain color.
Now, Safe-T-Sorb is probably the nicest looking product that is the same material, just a different color. STS is available at Tractor Supply stores. It is a blend of soft browns and greys. Looks very natural.
Turface is the same material, but baked to a uniform color. IMO their colors are too glaring for aquariums.
For more info about this group of products look for some posts with Safe T Sorb or Turface in the title.