Long fiber sphagnum moss by itself or long fiber sphagnum moss with a mix of sphagnum peat moss, pumice and some orchid bark is my choice for potting media. It holds moisture, drains easily, and is easy to work with. Especially when repotting. However, I have some Nepenthes in a mix of sphagnum peat with some perlite and orchid bark and they're doing fine. I've used an orchid bark mix with Nepenthes and that seems to work fine too. I think there's a recipe for every species of Nepenthes out there it seems! Sometimes it's hard to find pure long fiber sphagnum because many nurseries don't carry it. If that's the case, then I use the sphagnum peat moss with some pumice rock and orchid bark to help with drainage.

Sphagnum peat moss is cheaper and easier to get than pure long fiber sphagnum moss. The downside of sphagnum peat moss is that it takes longer to hydrate than long fiber sphagnum and falls apart more when repotting thus possibly disturbing the roots. Just to give you an idea of the diversity of soils out there from growers I've purchased Nepenthes from have used recipes from peat moss and perlite, all bark, sphagnum and perlite, pure long fiber sphagnum, to a mix of everything in between. I usually use long fiber sphagnum in the bottom portion of the pot so the mix doesn't fall through the holes. Then I fill the the other 1/2 or more of the pot with a mix of sphagnum peat moss mixed with pumice rock, some smaller orchid bark, and a little long fiber sphagnum moss mixed in. Then I put long fiber sphagnum moss on the top portion of the pot. The moss on top helps me judge how wet or dry my soil is and also lets me judge the health of the plant. Generally speaking, if the moss is doing real well the plant should be too. If the moss is black and not looking good then your plant could be too wet. Vice versa if the moss is overly dry. Be sure to hydrate all mosses well before potting up.

Nepenthes are very adaptable to a variety of soils. Every grower seems to have his or her "personal" recipe. So if you like the quality of plants you're receiving from your vendor why not try what recipe they are using. Oh, and don't use that decorative Spanish Green Moss stuff. I've been told that can be death to carnivorous plants. Long fiber sphagnum can be bought from Cal West Orchid Supplies. They deliver quickly, reasonably priced, and have many different sizes of sphagnum moss available.