OK. I've always been told not to have clams or sponges exposed to air. Never felt the need to test it out with one of my own clams
Learn something new every day. Thanks Brad for this info. I still don't have the nerve to leave my clams sitting out for half an hour.
Corals, I'm not so worried about. When I'm fragging or doing a big water change, the corals may be exposed for more than a few minutes, usually with no ill effects.