Best Gfo Media For Reef Tank Phosphate Removal

How To Use Best Gfo Media For Reef Tank Phosphate Removal

GFO is an important tool that should be an integral part of the regular maintenance of your tank. The function of Granular Ferric Oxide (GFO) can be to stop the growth of algae by eliminating phosphates from the aquarium. A low level of phosphates can help to keep algae from spreading and will also help reduce growth. An outbreak of algae is among the most frequent reasons for a tank shutdown.

What are the terms used to describe the best GFO media for reef tanks? As an enthusiast of aquariums, You’ve more than likely heard of GFO for reef tanks or granular ferric oxide at times.

Granular Ferric Oxide is a filtering chemical that is utilized in a reactor that inhibits the growth of algae in reef tanks by eliminating the phosphates in the column of water. There are two kinds of GFO media that are available. They come with the standard absorption choice and the high-capacity GFO range.

For those who are thinking about setting up a reef tank or want to expand their understanding of this field, D-D RP-100 ROWAphos is the best GFO Media for reef tank phosphate removal – 1000 ml/2.2 lbs.

D-D RP-100 ROWAphos Phosphate Removal Media - 1000 ml/2.2 lbs
  • Extremely high binding capacit
  • Needs very little room in the filter syste
  • Simple Handling (filter bag include
  • No influence on p
  • Does not release toxic substances back into the aquarium when exhauste

Last update on 2023-12-08 / Affiliate links / Images from Amazon Product Advertising API

Making use of GFO to build a reef tank correctly is not difficult to do. It’s quite simple once you’ve tried it a couple of times. Make sure to read the instructions in the GFO media you’ve purchased to ensure that you are using it correctly. It is the GFO I’ve relied on and recommend washing it prior to use. Here are the steps I adhere to. In the beginning, you’ll be required to put the recommended amount of ferric oxide granular in its GFO media bag and then secure it with a strong clamp.

There is the option of either washing the large capacity GFO using RO/DI water or placing it in a faucet permitting the water to flow over it in a fast flow until it becomes clean. Once it is time to install the GFO in your tank, you should select an area that is able to allow the greatest flow of water. Although it is recommended to alter GFO media every four to eight weeks, I would suggest changing the GFO medium every 4-8 weeks, I would suggest to do it whenever your levels of phosphate are beginning to increase or you are able to observe algae growth in your aquarium.


When you are using GFO initially, it’s not unusual for the initial batch to be exhausted quickly as a result of the initial high phosphate levels.

Keep track of phosphates with the test kit, and then swap in the GFO media when levels begin to increase at times as early as 7 days.

Once the first batch has been removed, the subsequent batch made of GFO will last for a longer time typically within the 4- 8 weeks period as explained below.


  • Begin with 1 tablespoon of 4 Gallons of water(16 Tbsp = 1 cup).
  • After 4-8 weeks, the aquarium will have adapted to lower levels of nutrients as well and the quantity of GFO may be increased to 2 teaspoons in 4-gallon water.


  • Begin with 1 tablespoon of 8 Gallons of water
    (16 Tbsp = 1 cup).
  • After 4-8 weeks, the aquarium will be at low nutrient levels as well and the quantity that is GFO may be increased to two tablespoons for every 8 gallons of water.

For Use In A Filter Media Bag:

  1. The GFO in the bag, and secure it
  2. Rinse the water with RO or set it under a tap until the water is clear
  3. Set up in a high-flow region of the sump or tank to ensure maximum flow of water through the GFO
  4. Monitor phosphate levels on a regular basis and change the GFO media whenever the levels of phosphate begin to increase (typically each 4-8 weeks)

For Use In A Upflow Media Reactor: Recommended

  1. Place GFO in the appropriate medium reactor
  2. The return line of the reactor into a sink or bucket
  3. Switch on the feed pump to flush out the dust and fines from GFO. GFO till the GFO is free of any trace.
  4. Install the media processor on your tank. Place the return line correctly into your sump or the filtration
  5. Reduce the flow rate through the reactor to ensure that the GFO barely twirls onto the floor. Don’t allow the GFO to tumble vigorously.
  6. Check phosphate levels frequently and change the GFO media as soon as the levels of phosphate begin to increase (typically each 4-8 weeks)

Are Media Reactors Worth the Investment?

GFO also known as Granular Ferric Oxide is designed to eliminate phosphate from the water of aquariums. It can be utilized as a treatment tool or instrument to lower phosphate levels however it is safe to use for daily use in aquariums with high bio load, where phosphate levels are not controlled by other methods of filtering.

GFO media is sometimes sold in a GFO bag, or you can purchase the media on its own and use it in the aquarium.

It’s okay to utilize your GFO in this way as you ensure that the GFO bag is in an area of your back chamber or sump that has a lot of flow. But, you’ll get better results when you insert the GFO media in the device for media processing.

The process of making use of GFO inside a processor is quite different. First, you will put the GFO in a suitable reactor. The return line will be left for the reactor to rest in a bucket or sink.

Clean the lines completely by activating the feed pump, allowing the water to flow until it’s completely clear. Place the reactor in your tank. Adjust the flow you are experiencing through the reactor until you can see that the GFO can be seen to just barely fall on the tank’s surface.

It is essential to be attentive to the flow, so it ensures that the ferric oxide does not rapidly tumble, resulting in the water becoming cloudy. This is a common issue aquarists can encounter simply making use of GFO media bags. GFO media bag method.

Do I need to use excessive GFO?

Absolutely! It is important to be aware of your levels of po4 and make sure you use sufficient to maintain your levels in control, but not anymore. If you use too much, it may become too aggressive with the removal of nutrients and can cause necrosis. This is usually the case on SPS. It’s also expensive, therefore making use of more than you need isn’t cost-effective, or will be beneficial.

If you opt to use the Granular GFO to treat an aquarium with a reef it is recommended to begin by adding 1 tablespoon of GFO for every four gallons of water you wish to treat. If everything is according to plan, you’ll be capable of increasing the amount of GFO by two teaspoons for each of the four gallons of water that you are treating.

If you’re working with HC GFO, start by adding 1 tablespoon of GFO for every eight gallons of water. Within four or eight weeks alter the GFO to add two tablespoons per eight Gallons of water.

While this is the dosage recommended it is still advisable to take your time and keep track of the levels of phosphate to make sure you’re getting the results that you have been trying to achieve using a tester kit.

Proper Placement Of Media Reactors

The proper placement of the large-capacity GFO reactor was my biggest challenge. I was confused when I first set in my setup. This is why I’d like to give you the lessons I’ve learned to you to help you avoid the same confusion I experienced.

When you set in place your GFO reactor, the pump should be kept apart from the pump of the skimmer. It is best to set the GFO reactor in the return area in your sump. But, make sure you leave room to the left of the return pump for the wealthy.

This will ensure that you’re not wasting time recreating the water that is already by this GFO process.

When Cutting Corners Can Be Costly – Best GFO Media For Reef Tank

There are several methods that you can revive a previously used GFO. This is however an intricate process that requires a certain amount of knowledge and expertise.

The process of regenerating GFO has caused a lot of harm for some aquarists. Be sure to take care and be aware of the precautions that should be taken since you’ll often be working with hazardous chemicals involved in these processes.

An alternative that I’ve chosen with fantastic outcomes is to use ROWAphos GFO. This product has the highest absorption capacity for treating silicate and phosphates that can harm the life of aquariums.

Even with some time prior to replenishing once that GFO media time has ended, I’ve noticed that my silicate and phosphate levels don’t immediately start to increase.

When I switched to D-D RP-100 ROWAphos GFO, I saw immediate improvements and improved coral coloration. my levels were fairly high before I began using GFO!

When Cyano is Lurking

I have recently experienced an issue with cyano, the red algae, growing quite quickly inside my tank. I discovered that it was happening due to the high levels of phosphate that were present in the water.

This was when I discovered the importance of using the correct amount of GFO to maintain an aquarium that is healthy. To compound the issue by examining the conditions of the water I discovered that the levels of nitrates were also high. This led to the speedy cyano-growth within the tank.

While GFO for reef tanks can be a great start in getting rid of the problems that come up with cyano, I soon realized that it’s not enough by itself. If you encounter similar issues in your tank, you should remove as many green algae as you are able to.

Increase the frequency of water changes, and then start creating your own RO/DI water to mix your salt, Spectrapure is an excellent choice for that. Improve the flow in your tank’s reef in stagnant spots, and also through the sump. It also reduces the amount of water that is fed to it.

Incorporating a reactor to make bio-pellets will aid in decreasing the number of nitrates in your system in the absence of an aeration system, however, they will not do anything to improve the levels of phosphate.

Therefore, it’s a smart idea to utilize two high-capacity GFOs as well as bio-pellets in concert to complete the job in the right way, particularly when there’s no refugee certainty.

All debris that is in the rock pores while you’re running on the GFO filter bag or the mechanical filter must be removed.

A refugium with macroalgae can increase the flow of nutrients, which will help to eliminate the mess faster.

We all know, that faster is more effective in these scenarios. If you don’t have sand-shifting creatures and pods inside your tank, you should consider buying them, as it improves the sand bed’s functioning in your tank.

The GFO & Carbon Debate

You may be worried about using the granular ferric oxide along and carbon Don’t be. They are designed to complement each other when used correctly.

Although I do my best to be careful in everything I do in my aquarium, which is suggested, I’ll admit that I’ve taken shortcuts.

In addition, you can daisy-chain the GFO reaction and carbon reactor it is also possible to put these components together into one unit.

This can get confusing when you learn the carbon has to be replaced every two weeks, whereas your GFO is advised to be replaced at least every 4 to 6 weeks. With the sponge included with the purchase of your reactor, you will be able to remove your carbon from the GFO within your reactor. Be careful, as it can be messy.

Precautions you should be aware of when using GFO

Inadequately monitoring the levels of phosphate regularly could lead to significant setbacks you’re trying to avoid.

A lot of GFO reduces the phosphate level significantly which causes the alkalinity level in your water to decrease. check your Alkalinity before you begin making use of GFO.

If you boast of beautiful Chaeto in your refuge Too many GFOs also kill this.

If you find that your chaeto is dying and you are concerned about it, don’t let it persist. Remove the dead chaeto. This will help to improve your phosphate level, as well.

In the end, you’ll be satisfied that you took the time to find out how to use the ferric oxide medium as well as other maintenance solutions that are discussed in this article. If you’d like to know more you can keep following ReefHacks to enjoy the benefits of a beautiful and healthy aquarium that is flourishing.


What is the best way to lower phosphate in a reef tank?

The most commonly used method to lower the phosphate levels in your tank is using a binding media such as clay. If you are looking to reduce the amount of phosphate in your tank, you could make use of granular ferric oxide (GFO) which is a phosphate absorber as well as the collector.

What neutralizes phosphate?

Chemical precipitation is used to eliminate the organic phosphate forms through the addition of a coagulant as well as a mix of coagulant and wastewater. The most multivalent metal ions frequently used include aluminum, calcium, and iron. Calcium is generally used in the form of lime Ca(OH)2.

How much GFO do I need per gallon?

Initial starting dose = 1 gram/gallon in media bag or fluidized reactor. Begin slowly as GFO gets rid of phosphates quickly and effectively, avoiding shock to your aquarium.

How long should GFO last?

GFO is typically able to last between 4 and 8 weeks in normal tank conditions, however, it can be longer in situations where phosphate levels are high.

Does Gfo lower alkalinity?

Drop in Alkalinity or Drop in pH. The issue is that when aquarium water comes in contact with GFO small quantities of the precipitate stick onto the surfaces of GFO and reduce alkalinity, which decreases pH.

How often do you have to run a GFO?

Change GFO as soon as phosphate levels begin to increase. It is usually every 4 weeks for the standard GFO and more than eight weeks with high capacity GFO.

Should I run carbon and Gfo?

While they all eliminate waste, they are utilized in different phases of the process of eliminating waste… Active carbon eliminates organic matter whereas GFO is primarily used to remove the phosphates… as well this is why it’s beneficial to use both of them in the aquarium of a reef.

Will GFO help with cyano?

While GFO for reef tanks is a good first step in solving the issues that are encountered with cyano, I soon discovered that it’s not enough by itself. If you experience the same problem in your tank, you should get rid of as many green algae as you are able to.

Will Gfo drop PH?

It is not uncommon to see PH decrease with GFO. GFO. Particularly in smaller tanks, or when large quantities are utilized. Sometimes, using less than the amount recommended is needed.


GFO (also known as Granular Ferric Oxide is designed to get rid of phosphate in the water of aquariums. It can be utilized as a treatment or tool to reduce phosphate levels that are too high however it is safe to use for daily use in aquariums that have a high bio load, where phosphate levels are not controlled by other methods of removal.

Each tank is distinct and distinct in regard to the proper phosphate levels. We have found that the majority of tanks between 0 and 3 years old must be kept at phosphate levels lower between 0.01 and 0.04 PPM for the best outcomes.

Aquariums that are more mature and have been operating for two to three years or more and have a large colony of corals that are mature can be run with higher levels of Phosphate without any issue.

Although phosphorous is essential for corals, fish, and other beneficial bacteria to develop and flourish in your aquarium, it shouldn’t be allowed to accumulate in the aquarium in water as a waste product.

The management of phosphates revolves around balance and stability, determining the ideal level for the tank you have, and avoiding allowing the levels to rise continuously. It is not a good idea to deplete your tank completely of phosphate however you shouldn’t allow it to rise beyond control.

The presence of phosphate in the blood can indicate an increase in nutrient levels altogether. It is a sign that nitrate levels are increasing too and you need to be aware of the bioload you are putting into your body.

These nutrients could contribute to the proliferation of nuisance algae and numerous other pests (cyanobacteria and dinoflagellates). Research suggests that phosphates inhibit the process of calcification in corals. This means they will slow their growth in higher amounts.

In contrast, if your tank is depleted of all phosphate, you may suffer from bacterial imbalances, which can deprive your corals and other important organisms of the necessary phosphorous.

The most significant source of phosphate is likely to be the coral or fish food items and the waste that results. Additives and media may help, but the amount of phosphate will usually be minimal compared to what your food intake is bringing.

Controlling filtration to remove the waste from fish and food is your main goal to control phosphates, but in the event that that doesn’t work, Bulk Reef Supply GFO filter media is our top tool.

GFO is not able to resolve an algae problem in its own way. If there is evidence of an algae outbreak take action immediately with an array of defenses that are specifically designed for the kind of algae you’re dealing with.

Here are some typical methods to help protect your aquarium against the growth of nuisance algae. Algae is a normal aspect of maintaining an aquarium. the inclusion of these strategies in your routine can assist you in avoiding issues with excess algae.

  • Manually removing and cleaning algae-covered surfaces
  • Make use of GFO as well as other strategies to keep the phosphate levels at a low level.
  • Add fish that are utilitarian and clean-up crew animals like blennies, tangs snails, crabs, and tangs
  • Reduce lighting times or carry out an entire blackout
  • Keep a more efficient water change schedule, and ensure proper maintenance of your filter
  • Tune and maintain your protein skimmer
  • Be aware of the tank’s input of nutrients through coral and fish food

Dibyajyoti Bordoloi is the creator and author of, a third-generation experienced fish keeper and owner of a successful pet breeding farm. He is also a member of the Center for Wildlife Rehabilitation And Conservation (Assam), the Marine Aquarium Societies of North East India, and the Kaziranga Nature Conservancy of Assam.