I use normal multi-purpose compost (potting mix) with added John Innes (potting soil) for Mexican Pings. The few that I grow seem to like the nutrients. I've tried non-organic mixes, but in my conditions growth is slow using these. I've also added calcium in the past, such as calci-sand, and I can't say that I notice any difference in growth rate but it makes a nice top dressing. Maybe the mixes I use have enough trace elements to mean that calcium is not required.