Abstract: A pre-filled and sealed filter bag, is provided including calcium carbonate material having fine pores and two sheets of filter paper having substantially similar geometrical shape and dimensions and defining an outer periphery. The calcium carbonate material is selected from coral sand, oysters shells and/or crab shells. A peripheral joint extends along the outer periphery of the sheets of filter paper and joins the sheets together substantially overlapping one another to define an inner chamber within the interior of the bag in which the calcium carbonate material is enclosed. Each of the two sheets of filter paper define within the peripheral joint an air and water permeable filter area of a minimum of 900 mm2. The weight of the two sheets of filter paper material constitute more than 1/8 (12.5%) of the weight of the material contained within the filter bag.