If you ran good anti-freeze, a radiator would be optimal. A steel tank, even with a 500GPH pump hammering water through it... will still start to freeze from the outside in. Good rad, good anti-freeze = subzero WC from mother nature.
Sure as hell won't have to worry about algae growth! The storm has gotten worse since that picture.
Notice the ice on the power lines? ... it was the size of a golf ball in that picture. Now the ice is the size of a baseball. The power lines look like core samples from a glacier or something...