Montmorillonite clay(safe-t-sorb, kitty litter,turface pro etc) are very, VERY light. You can use it as a stand alone substrate but you still would want to treat it like any other substrate like eco-complete, floramax etc. It has no nutrients so you'd want to add nutrients first or, before adding livestock(O+, root tabs). However, Montmorillonite clays are especially good at both absorbing and adsorping nutrients(high CEC). One problem I've read and been told about us the tendency for these products to kill your kh. So manual buffering on your part is a must. Or, you can use a Gh increasing agent BEFORE adding livestock.
Stock lightly and carry a big filter. - I don't have aquariums. I have ecosystems in a glass box. - Hygrophilaholic and hoarder of Anubias.