Wow, a 2007-2012 thread...way to dig up the past!
Actually, clay substrates do have a high CEC however even Special Kitty kitty litter is a little 'soft' and breaks down after a year or so. I prefer calcined Montmorillonite clay which is 'fired' longer to make it harder so it doesn't break down as quickly. I've used several different types over the years, the one I currently use is Safe-t-sorb (STS)
, a 40# bag is available at Tractor Supply Company for $6.49.
Here is a 10 gallon with STS, low light ([email protected]
), Ferts, no CO2 but Excel / glutaraldehyde