Pond Care Submersible Filter This filter is ideal for the smaller pond owner. It is submersible and provides the mechanical and biological filtration in a compact design that sits on the bottom of your pond. Provided with this filter is a non-woven, dual-action polyester filter pad which removes both large and fine silt and debris. The polyester filter pad has a coarse side to remove large debris and an ultra-fine layer to remove fine particles. A secondary part of the filter is the biological area where the beneficial bacteria grow to remove harmful compounds (toxic ammonia and nitrite). The filter comes with a multi-function fitting to accommodate a variety of hose sizes and convenient handle to remove the filter for easy cleaning. This filter comes with two pounds of Ammo Rocks.