i have successfully moved 5 different 75-150 gallon aquariums, and had them set up the next day using the same sand from the system. not saying it is the right thing, i just couldnt afford to buy a couple hundred dollars worth of sand. i always rinsed mine w/ the garden hose in a bucket, then let all the water drain out. i always save some that isnt washed for seeding purposes. again not sure if that is the correct way, but i bever crashed my system, but i have heard of people that had crashed doing it that way.