The purpose of granular ferric oxide is to inhibit algae growth by removing phosphates from the aquarium. Maintaining low phosphate levels will help prevent algae outbreaks and control growth. Serious algae outbreak is one of the most common reasons for complete tank shutdown. GFO is an essential tool and should be part of regular tank maintenance
Granular ferric oxide comes in two different types.
Granular GFO - requires the least amount of flow to tumble. Good for reactors.
High Capacity GFO -twice as dense as Granular or Pelletized GFO. This means twice as much material will fit into a reactor. It's extremely hard and has less dust. By volume High Capacity GFO will remove roughly twice the phosphate compared to Granular or Pelletized GFO. Best overall performance.