I figured that the aquarium forum is the obvious choice to ask questions about kitty litter (LOL). I've never had a cat and don't know anything about litter. I'm planning to mix kitty litter with peat moss for a plant substrate. Do any brands have any additives that are harmful to fish? What is kitty litter made of? I'm guessing that the cheapest most "un-special" brand is the stuff I want. Thanks!