How long can plants last out of water, but still wet. And do they need to be in a bag with oxygen? One more question, I have some S.Subulata and some E.Tenellus. I was wondering if i was to keep them in an area in my tank sectioned of with small pebbles, would this stop them from spreading like crazy, because they are pretty fond of doing so. Maybe dig the pebbles quite deep into the substrate? or would the roots still geow underneath them. My sand is 2-3'' deep. Help appreciated.