Help! i have some vallisneria spiralis which i want to plant in the back of my tank. i have sand substrate which is not very deep (an inch at the deepest maybe) and try as i can, i can't get it to stay planted. My other worry is that even if i did manage to get it to stay in the sand, my critters like to move the sand around and during pwcs surely it will get disturbed and float again. In fact that's what happened today, i had them planted and when i poured the rest of the water back in, they floated back to the top. Any tips or tricks?