Akadama can also be hard to obtain, for the last 6 years I have been using Cat Litter, not just any cat litter but one that is exactly the same Clay as Akadama. I live in Manchester England and have found 2 different types, one from Tesco super Market which is small Particles like AKADAMA HARD, but a different colour, more light brown than dark brown, it has on the pack TESCO LOW DUST, the other is from Pets At Home, called SANICAT PINK as it says it is a pinkish colour and this one doesn’t break down like Akadama, so you can use it like pumice