Buy a couple of bags of expanded clay. It is lighter than river rock and easier to handle. add it to the same plastic storage box shown. Put foam filter media on top to keep large particles from plugging it And help distribute the water over the expanded clay. It has a huge surface area for bacteria to grow on. It may take a week for the bacteria to take off an cover the expanded clay and make it into an effective polishing bio filter. It will keep your pond crystal clear. If you want to accelerate the bacteria growth onto the clay add a few ml of clean carbon into the pond....vodka. It won’t harm the fish. The water will cloud up a little from the bacteria explosion over the next few hours and coat the expanded clay with fresh bacteria. In a few more hours the water will be crystal clear.
