Filter Carbon Active is an active filter carbon for all pond filters.Filters fine dirt particles Removes odors and dyes Quickly clear pond water again Filter carbon is a highly porous material that absorbs unwanted substances from the water. Absorption is optimal due to a very large internal surface area.A combination of different filter materials is most effective in the pond filter. Place the filter carbon as the last medium in the filtration process. Fill the net with filter charcoal, rinse well and place the net in the filter. Check the material for saturation and replace it.