Aquatop Forza HOB filters are equipped three stage filtration. Each of the replaceable filter cartridges has activated carbon, a bio-plate for beneficial bacteria, and filter floss to polish your water. The Forza 40 - 80 also includes a surface skimmer to promote gas exchange at the surface. All filters also have built in flow adjustment in case flow rate is an issue in your tank.
Forza 5 - 15 is for tanks 5 - 15 gallons and has a flow rate of 45 GPH
Forza 15 - 25 is for tanks 15 - 25 gallons and has a flow rate of 80 GPH
Forza 25 - 40 is for tanks 25 - 40 gallons and has a flow rate of 120 GPH
Forza 40 - 80 is for tanks 40 - 80 gallons and has a flow rate of 240 GPH
Rivers to Reef says: You can use these for both fresh and saltwater, but remember salt creep is an issue with HOB filters. If you are keeping a fish only saltwater tank please consider using a canister. If you are doing a reef tank, please consider not using a filter.