We claim the ornamental design for a bulk seed tank, substantially as shown and described.
FIG. 1 is a perspective view of a bulk seed tank according to the present invention;
FIG. 2 is a perspective elevation view of the bulk seed tank;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
Applicants make no claim to the structure shown in broken lines in the drawings. Furthermore, Applicants note that the markings on the figures are for shading purposes only, and are not to be considered a part of the design of the present invention.