sand won't bother them, but they won't be inclined to spend much time in very sandy soil - they need some 'grit', but they like lots of organics and the microbial life that goes w/ it - if you're thinking of adding worms to a potted plant, not much point, they'll find their way to greener pastures!

Bill

I composted with my worms without adding sand for 18 months, and they were pretty slow at creating the black gold mulch stuff.

I added a few handfuls of sand to each of my five or so bins a couple of months ago, and it the worms are grinding their food into castings much faster.

Wow, Hebd, that's great. I'm going to try that.

If you really must add a couple worms to your potted plant, make sure to keep a layer of mulch on top of the sandy soil. Leaves, some shredded cardboard, basically what you might find the worms living under in the wild.
How big is this flower pot? If it is too small and drys out completely the worms will bail.