The ornamental design for a safetycap for fish-tank siphon, as shown and described.
FIG. 1 is a top perspective view of a safety cap for fish-tank siphon showing my new design;
FIG. 2 is a bottom perspective view thereof;
FIG. 3 is a front elevated view thereof;
FIG. 4 is a rear elevated view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a right elevated view thereof;
FIG. 8 is a left elevated view thereof;
FIG. 9 is a reduced top perspective view thereof, showing the safety cap for fish-tank siphon attached to a transparent siphon; and,
FIG. 10 is a reduced bottom perspective view thereof, showing the safety cap for fish-tank siphon attached to the transparent siphon.
The broken lines showing of a transparent siphon in FIGS. 9-10 are included for the purpose of showing environmental structure and form no part of the claimed design.