Pack of two algae removing replacement cartridges for the aquarium systems cobra internal filter range or any internalexternal filterr newaqua algo out is a special anionic resin unique of its kind its chemical characteristics and the fact that it is particularly macroporous enable it to eliminate nitrates selectively and stop algae growthr the particular dimensions and spherical structure of newaqua algo out prevent not only compacting inside the filter but also guarantee a perfect contact