Any help please....i went in to the wendy house to let the rabbits in the garden this morning & i was shocked to see their water had frozen in the bowl, they had broken it to get to the water but it was thickish ice, i had been in to them early hours at 2am this morning & it was fine but at 8am it was frozen. Can you please tell me what you use to stop the water from freezing as it is going to be an other cold night