Jurassic sand is the best stuff out there for Nephrurus, although you can use pretty much any washed natural sand it work just fine. Stay away from Calcium based sands the stuff is garbage.
I use Jurassic Sand and I think its great. Its suppose to be very fine without being dusty; I read somewhere that said every grain has round edges, so its less harmful even if swallowed.
I use the same sand in all of my tanks now and have never had any issues. I use natural Desert sand, i buy big 4kg bags and the sand is quite damp, i throw it in the tanks, smooth it out, put in all the furniture and stuff and when in dries its very compact and hard so there isn't much loose sand. Its natural, easy to clean and doesn't have an odor.