If you're going to feed it out the viv when it's younger i'd say sand would be ok. It's when they're really small or clumsy and they go to catch a bug and get a mouthful of sand thats where the trouble starts.

Some people just don't like it but i cant see a problem if you feed out the viv til they're a bit bigger. Then maybe put a little tub in the viv to keep the bugs in so they're not eating directly off the sand.