Filter for Pet Fountain

FIG. 1 is a front, right and top perspective view of a filter for pet fountain, showing my new design; FIG. 2 is a rear, left and bottom perspective view thereof; FIG. 3 is a front view thereof; FIG. 4 is a rear view thereof; FIG. 5 is a left side view thereof; FIG. 6 is a right side view thereof; FIG. 7 is a top plan view thereof; FIG. 8 is a bottom plan view thereof; and, FIG. 9 is an enlarged detail view of portion 9 encircled in FIG. 1 . The dot-dash broken lines depict the boundaries of the enlargements that form no part of the claimed design.