Ive had a piece in my tank for almost a year fully submerged, not doing great but not dying, I had a friend though who had several pieces fully submerged that were growing roots and leaves, the roots came right out of the side and looked really cool draping down, he did all this with a 25 watt light, the tank was also horribly overstocked and he never did water changes, but his live bearers were doing great and shrimps were bright red. We think its because he was a Buddhist!!