Think Truck will have to answer that one for you... But I will add my own question... Do you have to cap the cat litter with sand? or can you leave it exposed to the water column?
i) Tesco value - grey colour. I just poured it into a empty bucket from a height of two feet to remove the fine dust. When water is added to it it will go expand and go soft. I then capped it with sand. Plants grew well in it but its very messy to remove and re-scape with.
ii) Tesco Premium - red colour. This needs to be wash very well as it has a deodorizer added and is very dusty. This has a look of akadama but is a lot harder and hasn't soften at all. This I didn't top at all and holds plants down well and doesn't make a mess like the above. Plants are doing well