The ornamental design for a laboratoryfishtank, as shown and described.
FIG. 1 is a perspective view from the top end, front and right sides of the tank;
FIG. 2 is a front side view thereof;
FIG. 3 is a back side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a left side view thereof;
FIG. 6 is a top end view thereof; and,
FIG. 7 is a perspective view from the top end, back and left sides thereof with the tank lid positioned off the top of the tank and in the back end lid holder.
No bottom end view is shown because it is hidden when placed on a table-top.
The broken lines showing environment in FIG. 1 are included for illustrative purposes only and form no part of the claimed design.