I usually use a pretty sterile soil so I always have a low dose of fertilizer in the water I give them. I use Dyna-Grow. My potting soil is a mix of some, but not necessarily all, of the following: pumice, sand, perlite and high-quality potting soil. It varies with the plant being potted, whether they need very quick-drying, fast-draining mix or are a little more tolerant. Some growers say don't use sand, it holds moisture. Haven't made up my mind on that yet.

Anna

I use Builder's Sand, bought at HD on my C&S's..Potting soil, sand and Perlite..about 1/3rd of each..it's well-draining and does the job.
But if you decide to go w/sand, don't buy play sand..that DOES retain water.
Depending on the mediums you use, in other words if you use Perlite/sand/etc, w/o potting soil, you should fertilize..If u use the potting soil, you can wait a while before adding nutrients, since most potting soil contains nutrients..
They also sell C&S soil but if you've a huge collection of plants, it'll add up in cost.,.
As for fertilizing, I use Fish Emulsion, C&S fertilizer or well-dilluted all purpose. Not at the same time, of course..I alternate. Good luck planting..Toni