Enriching sand substrate?
I have the opportunity to change my tank substrate, and have questions. I plan to go from gravel to black diamond blasting sand, and was planning to use cat litter to enrich, but I recently realized that as an art student, I have access to free powdered clays, from Red art, Sillica, Yellow Art, Bentonite, OM4 Ball Clay, Kaolin EPK, Sagger, Molochite, Black Iron Oxide, Red Iron Oxide, and hundreds of other powders. Anything else I should use, or definatly not use?
I also would like to not use any gravel in my new tank, but am worried about not seeding the new material. Should I use some in the bottom layer of the substrate, where the clay would be?
Could anyone recommend a recipe with proportions of what to use, to enrich my sand in order to grow low light pants well? Is it even worth it?