@camilio81 thanks for your kind comment. Duplicating their natural habitat became a real challenge since I live in the tropics. This took two repotting before I got it right. Soilmix was coco peat, pumice and akadama, all in 1:1 ratio, and plenty of plant food made of ground neem and frass. Toppings are river rocks. I am not sure though, but the supplier said that their river rocks slowly break down in two years and enriches the soil with minerals.
Thank you! I’m in the states.. Tennessee. It’s cold here right now and mine are inside under grow lights. Hopefully they do okay. Mine are just in a mixture of pumice, cactus soil, and rock. Super fast draining.