Plastic shoe box, fountain pump w/bell fountain head, some plastic screen and quilt batting.
Drill 1/2in holes all over box, plus a hole in the lid the right size for the fountain pipe to go thru.
Place screen around fountain pump so batting won't be pulled into pump, place pump in the shoe box and surround with batting.
Put top on securely.
Place in pond with bell shaped fountain head (gives most surface area and spash), turn on.
Keep filter away from edge of pond. (if it gets knocked over it will pump out whole pond)
If running right, check every day and make a note of how dirty filter is getting.
Clean filter when bell size starts to decrease. ( after this point it will clog fast)
Adjust sizes accordingly.
Happy filtering.
Dr Joe