I claim the ornamental design for an aquaponic tank, as shown and described.
FIG. 1 is a front isometric view of the aquaponic tank.
FIG. 2 is a front elevational view of the aquaponic tank. The left and rear elevational views are the same.
FIG. 3 is a right elevational view of the aquaponic tank.
FIG. 4 is a top plan view of the aquaponic tank; and,
FIG. 5 is a bottom plan view of the aquaponic tank.
The surface shading in FIGS. 1-5 shows contour of the three-dimensional aspects of the design. Portions of the aquaponic tank shown in broken lines form no part of the claimed design.