I need to have some hind of weight to hold down some Wisteria stems until they root. Nobody around here sells plant weights. I have had a couple of ideas but I' m not sure if they would be safe. The first one was to cut the ends off a large sewing needle and tie the stems to that. It would be easy to push down into the gravel. My second thought was to use a twist tie from a loaf of bread and wrap it around the stems. I'm sure either one would work but I don't know how safe it would be for the tank.