Am considering a trial tank with WalMart Kitty Litter seeded with Osmocote as first layer, Flourite as middle layer , then sealed with gravel (and maybe coarse sand) . 1. Any recommendations as to the amount of Osmocote to use in the KL layer (Per unit surface area)? 2. Comments re the adviseability of this whole approach? Thanks, Norb Spitzer Carlsbad, CA