GFO stands for granular ferric oxide, and those who are starting with an aquarium may have heard that this chemical can be used to prevent the growth of algae in reef tanks.

GFO works by removing phosphates from the water column. If done correctly, it can be beneficial at hindering algae growth. However, beginner reefers need to understand that there are a few things you need to pay attention to, to get it right and not cause any accidental damage to your tank.

Why are algae harmful in an aquarium?

Some algae growth is positive in an aquarium as it helps to stop dangerous levels of nitrogen having a toxic effect on the life forms that live within it. However, too much of a good thing, unfortunately, holds true when it comes to the presence of algae in an aquarium as when it dies it releases the nitrogen back into the water.

GFO – how should it be used?

Using GFO to support a healthy aquatic system is a smart move. The easiest, and perhaps most obvious piece of advice is to make sure you read the instructions on how to use it as these may differ from product to product. However, some general tips can help ensure GFO in your tank is as effective as possible. These include:

Rinsing the GFO before use until it is clear.

Ensuring that you pour the recommended amount into the media bag and that the bag is fully secure before putting it in your tank.

Using common sense when changing the granular ferric oxide. While most products recommend changing between 4 – 8 weeks, if you notice algae levels on the rise, do it sooner. 

Use a phosphate test kit to measure phosphate levels in your aquarium.

Make sure you place the media bag in a location of your sump/back chamber where the water flow is robust.

Should you use a media reactor?

A media reactor is likely to be the most effective way of releasing GFO into your tank. If you decide to use one, you first need to flush the line. To do this make sure that the return line for the reactor is placed in a bowl/bucket or your sink and turn on the feed pump. Wait until the water runs clear. 

Once this has been done, you can place the media reactor in your tank and then change the flow so that the GFO is only very lightly rumbling onto the surface. If it tumbles too vigorously the water will go cloudy, so make sure you monitor this carefully to avoid adding too much. 

Where you place the media reactor is crucial, ensuring that the pump of the reactor is apart from the skimmer’s pump. Ideally, set it into the return section of the sump while still leaving ample room for the effluent, so you avoid re-treating the same water twice. 

Can you regenerate GFO?

More experienced reefers may wish to try regenerating GFO, but it is essential to emphasise that if you don’t do this properly your aquarium could suffer severely as a consequence. Remember, you are dealing with potentially hazardous chemicals, and therefore, proper care and precautions should always be taken. 

Can GFO treat Cyano?

If you’ve noticed red algae growing in your tank, this is likely to be Cyano, and while GFO can help to reduce the levels of it and slow growth, you may find that GFO alone won’t be able to keep it under control. To tackle this problem, it’s advisable to first vacuum out as much of the red algae as possible, increase water changes and consider a water filter system such as SpectraPure to help reduce the amount of Cyano in the tank. A combination of high strength GFO and bio-pellets is usually very effective. 

Should I use granular ferric oxide and carbon simultaneously?

You may have heard warnings that GFO and carbon shouldn’t be used in the same reactor, but they actually are designed to complement one another, and carbon will ensure that the GFO doesn’t bind together. Carbon does, however, need changing more frequently than GFO, so to get around this separate the two using the sponge that comes included with the reactor. 

GFO – it’s all about the levels

Getting the levels of GFO in your aquarium right is important. If you put too little in it won’t be effective at reducing the algae, however, if you put too much in you could decrease the levels go phosphate too much, causing the alkalinity in your water to drop significantly.

Creating the perfect habitat for your coral takes time and practice, however, using GFO correctly is so worth it. Use the above as a guide, take your time, and you’ll be glad that you did. 

If you are looking for stunning coral frags for your aquarium check out our shop, or if you have any questions about how to get the most out of your tank, contact us using the contact form, and we’ll get back to you as soon as possible. 

This site uses cookies to offer you a better browsing experience. By browsing this website, you agree to our use of cookies.