First, drain the water from the fountain. Use an old chisel along with a wire brush to remove any loose material along the length of the crack, wash with a mild detergent and rinse with fresh water. Once the concrete had dried, inject the crack at the inside of the fountain with epoxy filler.

No action should be necessary at the exterior unless you wish to conceal the crack. If so, clean the outside as suggested above and caulk with a latex caulk. Use a damp sponge to wipe away the excess caulking.