Forget the kitty litter if you live in the US. Look for Turface MVP, it is usually sold at John Deere Landscaping stores here.
Hey John,
I have seen turface mentioned a couple of times, but never actually seen it. What sort of stuff is it? Bob is in London area, UK.
Bob: You have mentioned in one of your posts the same stuff that Auk and I use in our mixes, through a link on cat litter on bonsai4me.
I have moved away from using it as only component in the mixture as I find the topsoil stays moist too long, and I get algea (Through my rainwater drums that are not fully light-proof). I am now mixing it in with dry levelling gravel, effectively this is expanded backed clay, crushed to 1-3-5mm particles.