Bake and cool 8 x 2 in. cake. Use spatula and white icing to ice cake smooth.
Transfer fish pattern on cake top with piping gel. Use tip 12 and yellow icing to pipe circular lines for body. Use tip 5 and white icing to pipe dot eye. Use tip 3 and black icing to pipe dot pupils. Use tip 12 and green icing to pipe bead gills, fins and tail. Use tip 5 and orange icing top pipe bead mouth. Use blue icing to pipe tip 12 dot bottom border and tip 5 random dots on cake top and sides.