Anodonta cygnea large
Swan mussels are British native molluscs. They are filter feeders, passing pond water through as they rest at the bottom of the pond and filtering out pond waste, thus helping to clean the water. They must have gravel or mud in the bottom of the pond in order to keep an upright position so that their bivalve system can operate. If a mussel dies it should be removed or it will decay and pollute the water.