I've got a few Lithops, Conophytums etc. They just seem to survive in nothing, I've found they grow very well in pure clay granules, or even fine grit, with perhaps a couple of weak feeds when in growth each year. I've got some better pics but need to find them.
Pete, Looks like Lithops pseudotruncatella. I find that they have deep roots systems and actually prefer relatively deep pots. People often grow them in small pots, but I find the heads are smaller than if grown in a bigger one.
I must admit I quite often am amazed by the size of the root system. But mine,(these days) survive on total neglect, so I think most of the fine roots are just annual, shrivelling back to just the main root when dry.
