n tropical streambeds, aquatic plants are found growing in a special clay called Laterite.  FIRST LAYER is an all natural Laterite in a granular form, which is ideal for aquarium use.  The pure Laterite in FIRST LAYER provides the perfect planting medium for a natural aquarium.   Mixing all natural Laterite into the gravel bed creates an excellent planting medium for rooted aquatic plants.  Safe for use with tropical fish.