Denny - Go to Fleet Farm (or Farm Fleet in your neck of the woods) go to the farm section and pick up a $20 submerged stock tank heater - the one with the metal basket around it. I used this in my home-made acid tank (wood box and plastic sheet) until the snow started flying and I had to move the tank for plowing.
at the 40-60F range, the acid bath just takes twice as long.
Or pick up a 400W heat tape - wrap around the out-side of the rubber-made tote, put some insulation around it, then put that inside a larger tote to hold it all together.
Other suggestions I have are much more expensive....
Or you could switch to vinegar and bring in the house if you could stand the smell
