Those are beautiful guys and gals.
I would like to warn just from personal experiance not to keep them on the sand bed for too long. They can become prone to infections and irritations from the critters in the sand bed. Not a given, but taking a risk. They will do much better attatched to rock where they can get flow from underneath if they need it and they will stretch upwards and clean themselves if they feel so inclined. TO ensure enough flow needed on the sandbed the sand would be blown around.
Resting on a sandbed usually results in melting rics.