Tank frame

FIG. 1 is an isometric view of our design for a tank frame;

FIG. 2 is a rear view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a left side thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The portions of the tank frame shown in broken lines in the figures form no part of the claimed design.