GFO or Granulated Ferric Oxide is used in aquariums for removing phosphates. GFO is efficient in doing this by chemical reaction in which phosphate combines with the GFO, removing it from the water column. It will also bind together other organic compounds and certain metals that are not required in a saltwater tank, thus removing them from the water column. GFO is an oxide of Iron and is also considered as rust. Maintaining low level of phosphate in tank is very important if you want to keep a check on algae problems that bloom in the presence of phosphates. Growth of calcifying organisms like corals and coralline algae can be hindered by phosphates in tank.
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There have been many ways considered to keep phosphate level in check like introducing some bacteria and algae that consume these elements. However, the latest trend that many aquarists are using is use of GFO for binding phosphates and other harmful compounds. GFO has been used in purifying drinking water in mineral plants and is considered very safe and friendly element for the purpose.
Phosphate is known to bind to iron oxide hydroxide through a direct ionic interaction between one or two negatively charged oxygen ions on the phosphate with the ferric ions (Fe+++) in the solid. There are other ions too on the surfaces that are known to bind to GFO surfaces, including sulfate, chloride, calcium, magnesium, trace metals, and organics. GFO is said to be very fast in removing phosphates from a saltwater tank and effective result can be tested in just a few hours after the introduction of granules in water.
How to use GFO in tank?
There are two main ways of using GFO to bind phosphates. The most accepted method is using it in a reactor. Reactor pumps water from the aquarium into a tube of acrylic, gently tumbling the media, keeping it suspended in the water column. This process is preferred because it increases the surface area of GFO that the water is exposed to, thus increasing the quantity of phosphate it can bind to. Remember that since the chemical reaction occurs on the surface of the granule and not deep inside hence the surface area exposed to water matters a lot.
The other method is more basic, and uses a filter sock placed in an area of the tank or sump that has a higher flow. There are a few of shortcomings to this process. Since the GFO is packed into a filter sock, the amount of surface area is rigorously inadequate. Also, it must be a fairly small fine net sock that is used, as it can trickle through bigger openings and spread through the display tank. Another problem faced while using this process is caking that GFO forms a compact, brick like structure, which again, limits the surface area being exposed to the tank water. The only advantage to the filter sock method is the price.
Related issues
Adding GFO too rapidly to your aquarium can cause issues. There have been reports of coral stress, tissue recession, and bleaching. It doesn’t appear to be extensively understood why this happens, but many think the rapid depletion of phosphate shocks the system. It is also alleged the GFO may bind with trace minerals that coral need to survive, and because of the sudden drop in available minerals or nutrients, the coral becomes stressed. This all being said, it appears most tremendously think the benefit overshadows the risk of using GFO, with the caution to go slow and gradually increase the amount of GFO you are using. The amount of GFO that is needed is roughly one tablespoon per four gallons of water. Also, before using GFO, it is important to rinse it in RO water to remove the dust.
Disclaimer: Reliance on any information provided in the article is solely at your own risk. Reefland is not responsible for side effects of any process or product stated.
