A 401w pack of two new Aqua One Polymer Wool pads to fit the the top basket of the Aqua One Advance 550 and Aqua One Advance 750 external canister filters. Polymer Wool makes superb fine filtration material for aquarium use as it is capable of trapping even the finest particles. Aqua One Polymer wool inserts are safe for use in aquariums types including fresh and salt water environments. It cannot be reliably rinsed clean and should be replaced once per four to six weeks when your filter is cleaned out. Blocked Polymer wool will greatly reduce your filtration capacity putting your fishes lives at risk so do change as often as required.
