About 5 years ago, Sheridan Cleland of MyPDFscripts wrote the below article on his blog. Soon after, the site disappeared. I wanted to keep the memory alive, because these practices by the studios have not changed. They have only become worse.
Cacti are one of my favorite types of plants to grow inside all year and outside in summer. Unfortunately, the ambient air tends to stay moist during most seasons, a condition which makes cacti unhappy. Cactus potting soil can enhance drainage, increase evaporation and provide the dry conditions that cacti favor.
racor_2006. You should use a good potting soil that drains well. Do not use Cactus mix as it does not have enough nutrients. I use kelloggs Patio Plus and have used other organic potting soils. They do great in pots. I have them in 15gal pots with a pole as a trellis which it will need for support. Good luck.