I got some of the ebay mangroves recently. Now where I live its rather cold. So, by the time I got to the mailbox the groves were frozen. I thawed them out in fresh water and changed it a couple times. I put them in my sump. They are under a light on a rev photo from a tank. I know the leaves will fall from stress. How do I know they are still alive, and not adding to a slightly raised phos level?