Id be very cautious with the live sand. Anytime you disturb an established sandbed you create a cycle by killing off micro-fauna. I would definately store the sand in a seperate container with water and gentle flow and keep an eye on ammonia levels, dont re-use the sand if you detect any traces of ammonia. Best advice would be to use fresh sand and seed it with the old especialy if the old sand smells like rotten eggs or thouroughly rinse it and allow it to dry before using it.