GFO and Carbon Reactors are a great way to remove phosphate (PO4) and impuirities in your aquairum water.
GFO will remove PO4 from your aquarium water but MUST be used in a reactor to be used properly. GFO must tumble otherwise it will clump up and become less effective.
Carbon is a great media that will remove impuriities from the water and make the aquarium more clear. Carbon will also help remove harmful chemicals and metals from the aquarium water. It is always best to use Carbon and GFO in reactors which will help prolong the life of them and utilize them to maximum efficency.