i would notice my one GSP has sand on his back quite often. i would try and catch what its doing but never would catch him doing anything with sand so i would figure he was just playing in it. well a few weeks ago i added some nassarius snails to my sand bed. i put them directly in the sand so the puffers didnt see them. i was trying to be sneaky, not working... i caught my one GSP literally taking mouth fulls of sand, sifting the sand through his gills and taking another mouth full! then i saw my second GSP doing the same thing after looking at the one puffer. i did see one of my snails above the sand at the surface turned over. do you think my puffers found this snail, figured out it came from the sand and are now hunting the others? i put approximately 3 in a few weeks ago and added another 7 over the weekend. i was amazed when i saw what they were doing and realized that they were probably looking for other snails.