Open the pond filter box or bucket container carefully. If this is a used filter, remove all old filter media and discard it. Clean the whole container with clear water. Do not use soaps or chemical solutions.
Wash all DIY filter media with clear water before use. Do not use chemicals or soaps on any of them. Be sure the products you choose have no detergents or chemicals added. Be especially careful with sponges or pot scrubbers, as they are often impregnated with anti-bacterial solutions or soaps.
Place several small, angular rocks at the bottom of the filter container. This will support the rest of the filter media and offer a place for beneficial bacteria to colonize. These bacteria are essential for healthy pond water. The rocks will also help stabilize the position of submersible filters in the pond.
Pour a layer of plastic, Wiffle-style golf balls or bio-balls (plastic things specifically manufactured for filters), on top of the rocks. Any DIY filter media with a large surface area is ideal for more bacteria growth. Cubes of stiff plastic foam or pumice stones are other options. The open-cell design provides more surface area.
Add thin, plastic pot scrubbers in an overlapping layer atop the coarse DIY pond filter media. This is the first layer of mechanical filtration to trap detritus and debris from the water garden. These are made from the same material as more expensive filter media.
Roll up a length of cotton or polyester high-loft quilt batting that has not been treated with fire retardant, stain guards or other chemicals in a loose spiral. Place this on top of the other DIY filter media in the container. This material will easily filter out small pieces of debris from the water. It is relatively inexpensive and can be cleaned easily with a garden hose, or replaced as needed.