For Use With Any Size Hydro Professional Canister Filter; Can Also Be Used With Other Canister-Style Filters;Box Contains 3, 100Gm Pouches;Chemical Filtration for Freshwater Aquariums removes fine debris and detritus; Also helps to remove colors and odors to promote crystal clear water;Carbon Should Be Used As A Middle Stage Of Filtration;It Is Recommended That Carbon Should Be Changed Out Every 1 To 3 Months