Keeping Fish in Garage Over Winter

[bjbass]

Hey guys. I typically keep bait (common shiners) in my garage over the Winter months as bait for ice fishing. I don't have any problems other than it freezing during really cold days. The fish are fine, but it has broken a HOB filter by freezing solid and expanding. Also, I have an old unused acrylic sump that I was thinking about using instead of my rubbermaid storage container tank. I think that will crack with the expansion. Obviously I could heat it slightly, but is there something I can add to the tank to keep it from freezing? I know limestone creeks in the area stay "warm" in the Winter and don't freeze. Is there somewhat of a similar strategy for a tank? Some kind of additive or chemical?

 

[ocean]

How about a live stock tank heater? They sell them at farm stores, Tractor Supply, ect.