My 2 welsh harlequinn ducks love sleeping in their little pond (it's just a little metal dish/pool? 9 in deep by maybe 20 inches long), but it's starting to get down into the 20s and 30s at night and I am worried the water may freeze around them and they would get stuck or trapped. I read online where people have had this happen. Yesterday, there was some floating ice and a section of water about the size of my duck where it looked like she may have slept last night. What should I do they love their pond!