Pet water fountain filter

FIG. 1 is a perspective view of a pet water fountain filter showing my new design;

FIG. 2 is another perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a back view thereof;

FIG. 5 is a left view thereof;

FIG. 6 is a right view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof.

The broken lines depict portions of the pet water fountain filter and form no part of the claimed design.