for unwated hitchhikers I would lay down a towel place the rock on top and spray with fresh water for a few seconds. This usually promps what evers in to come out. Yes you can cure rock in a tank, but imo its better outside of the aquarium simply because you do not have to do as many water changes to the display at first. Many order rock off line; depending on whom and where the rock comes from you can get some really cool hitchhikers. My only opinion would be to cure like you have done in the past the tub or trashcan method with powerhead and water changes.