Hi Jen, Rather new to this but I'll stick my neck out and suggest that your new Gymno could be a gymno baldianum and twins to boot. Nice couple! Lets wait for some confirmation though:) Scott.

They are either Opuntia macrorhiza or Opuntia compressa.

That's one unusual plant! Optunias have glochids, the barbed, brown, tiny spines (a new "bunnyears" has been developed without these but generally optunias come with the little nasties). Stems are jointed, new sections growing from areoles of previous segments. Does that sound like your plant? Whatever it is, it's way cool!

Well everyone has their own preference. I use Al's gritty mix which is very popular in the container gardening forum. It's equal parts pine bark, Turface, and granite grit. Here's a thread with some pictures of it for size reference. Succulent Soil Mix Some of those ingredients can be a bit difficult to find, so another option is to just amend a standard potting soil with whatever grit you can find. Pine bark can be found at hardware stores (Home Depot, Lowes, etc) as mulch. You want the smaller stuff though, not the big nuggets. Perlite can be found at nurseries and many hardware stores as well. (Although I wouldn't want to use it as the bulk of a soil because it tends to float and looks a bit ugly to me.) Pumice or lava rock would be better choices because they look a bit more natural and are still lightweight, yet don't float. But I have not been able to find them in an appropriate size here. Granite grit I found at a couple of feed/farm supply stores. (You want grower, #2, or medium size depending on how it's labeled.) Whatever you find, I would suggest using 80-90% grit and 10-20% standard potting soil. Finding ingredients to make your own soil takes a bit of effort, but it is much better than bagged potting soils or even the so-called cactus potting soils.