Best gfo reactor comprehensive review of the top products onlineThe best GFO reactor is essential for keeping your tank clean, making them a necessary component for every coral aquarium. That is because reef tanks are prone to high levels of phosphates, and while it is beneficial to an extent, too much is harmful. GFO (Granular Ferric Oxide) works against it and removes phosphate in controlled amounts while inhibiting algae growth to ensure that your plants are healthy.

We curated a list of the top GFO reactors with reviews to help you find which one suits your tank requirements. So, let’s get into the list!

Comparison Chart

Name Dimensions (in Inches) Pump Included (Yes/No)
Two Little Fishies Phosban Filter Media Reactor

14 x 3 x 3 No
Reef Octopus Beginner Media Filter

17.9 x 12.9 x 4.9 Yes
ACCEL AQUATICS Filter Media Reactor

15.7 x 9.6 x 6.4 No
Innovative Marine Minimax Pro Series Media Reactor 11.8 x 4.4 x 4.4 Yes
AQUATOP MR-20 Multimedia Reactor

15 x 2.5 x 3.5 Yes

Best GFO Reactors: Product Reviews

Let’s get straight into our list of the best reef tank media reactors:

1. Two Little Fishies Phosban Filter Media Reactor

– Pros

  • Reasonably Priced
  • Flexible connections
  • Large media space
  • Easy installation

– Cons

  • Slow-speed power

If you are looking for a GFO reactor on a tight budget, the Two Little Fishies Phosban Filter Media Reactor is a considerable choice. It is one of the most reasonably priced options on this list and provides great quality for its price.

The reactor itself is made from a transparent material that allows you to watch it as it filters your tank’s water. It is enclosed in a decent plastic and acrylic build, so you won’t have to worry about any leaks or cracks as long as there are no hard impacts on this media reactor.

When it comes to filtration, this aquarium media reactor can fit a maximum of five inches of media height without any issue. It is primarily designed for use with PhosBan and can fit up to 200 grams. When completely filled, you can run the Two Little Fishies Phosban Filter Media Reactor at up to 20 to 30 GPH, which is slightly below most competitors, but the results are satisfying nonetheless.

Even at a lower flow rate, the media reactor is suitable for use in tanks up to 150 gallons in capacity. Moreover, if you have a larger tank, you can use multiple reactors depending on the size, and it will work perfectly in keeping your reef tank clear of unnecessary algae.

When it comes to installation, the GFO reactor is one of the easier ones. All the inlet and outlet fittings are flexible up to 90 degrees so that you can turn them according to your tank’s orientations and shape. However, keep in mind that it doesn’t come with a pump or tubing, so you will have to purchase those externally.

Check price button

– Overview

The Two Little Fishies Phosban Filter Media Reactor is an excellent device if you are on a tight budget. The media reactor offers decent quality and a large media space while reasonably priced. Moreover, it also has flexible inlet and outlet ports that make it very easy to install. However, the maximum flow rate is quite low at 20 to 30 GPH, which may not be suitable for all kinds of tanks.

2. Reef Octopus Beginner Media Filter

– Pros

  • Easy to use
  • Pump included
  • Tubes included
  • Large media capacity

– Cons

  • Quite expensive

The Reef Octopus Beginner Media Filter is an impressive, easy-to-use device that is ideal for reef tanks. It can be used with a wide variety of filter media, so other than using it as a GFO reactor, you can also use it with bio pellets or carbon without any problems. Its design is quite robust, so placing in or removing the filter media is much easier than other options.

The robust design is also highly beneficial when it comes to capacity, and you can fit a lot of filter media into this device. Moreover, as the filter media is easily interchangeable, you can get the most out of each type and keep larger tanks clean without any issues.

While using this device is highly beneficial, the large structure and capacity come at a price, making it the most expensive entry on our list. While it does provide you with your money’s worth, it might not be the best option if you are on a tight budget.

Although, one place the Reef Octopus Beginner Media Filter will save you money on is external purchases. That is because it comes with a pump and popping in the package, which is everything you will need to set it up. The pump itself is efficient, and while it does get a bit loud sometimes, it will keep your tank clear of algae.

Check price button

– Overview

The Reef Octopus Beginner Media Filter is a great GFO reactor that you can use in all kinds of tanks. It has a robust design and large filter media capacity, making it perfect for small and large tanks, no matter what media you decide to use. Moreover, it also comes with a pump and pipes making installation easier. However, it is the costliest option on our list.

3. ACCEL AQUATICS Filter Media Reactor

– Pros

  • Inverted conical bottom prevents clumps
  • Improves water flow
  • Impressive capacity
  • Unique flow patterns

– Cons

  • External parts not included

The ACCEL AQUATICS Filter Media Reactor is a feature-packed GFO reactor with various useful qualities. For example, it comes with a specialized design for increased water flow, unique flow patterns that improve media contact time, and many more features. This is why it is one of the most powerful and efficient options available in the market.

Starting with its design, it is crafted to increase the water circulation you get from your aquarium pump. The system is very efficient and is able to keep working even when hooked up to a smaller pump. It can save you money on an external pump and as it increases water flow by up to four times, ensuring your tank remains filtered and algae-free.

Along with the improved flow rate, this GFO reactor also has a unique design to improve the water-to-media contact time. It uses flow patterns that ensure that water has to pass through your choice of filter media multiple times. Due to that, this reactor is able to get the most out of your pump and filter media.

While filtration is one thing, a problem that many reactors have is that the filter media often begins clumping. ACCEL AQUATICS has fixed this with their inverted conical shape used at the bottom of the reactor. It ensures that the media isn’t able to settle at the bottom and keeps you safe from the trouble of cleaning any unnecessary clumps.

As for the device’s capacity, the ACCEL AQUATICS Filter Media Reactor has a media volume of 600 milliliters and can be used with various types of media such as bio pellets, granular ferric oxide, etc. The recommended flow rate for using this reactor is 150 to 400 GPH, which is more than enough for most medium-large tanks.

The only drawback you might find with this option is the lack of any accessories or external parts. It means you will have to externally purchase a pump and tubing to connect it to the reactor. That being said, even a small pump will work well with this device, so it shouldn’t cost you too much.

Check price button

– Overview

If you are looking for an all-in-one reactor package for your aquarium, the ACCEL AQUATICS Filter Media Reactor is a great option to consider. It comes with various unique features such as a smart design, flow pattern, and even shaped bottom that make it highly efficient at filtering water and keeping your media in pristine condition. However, you will have to buy a separate pump and tubing to get it running.

4. Innovative Marine Minimax Pro Series Media Reactor

– Pros

  • Easy instructions
  • Small form factor
  • Impressive build quality
  • Pump included

– Cons

  • Sometimes clogs

The Innovative Marine Minimax Pro Series Media Reactor is a great option if you are a beginner looking for a GFO reactor. This option comes with clear and simple instructions that will make using the reactor very straightforward. Moreover, it’s recommended media is easily available online, so you can always make sure that you are using your media reactor correctly.

One of our favorite things about this device is its compact size. With dimensions of only 11.8 by 4.4 by 4.4 inches, it can easily fit into most tanks, even if you have lots of coral and decor. However, while a common concern with smaller reactors is that they won’t be powerful, this is not the case with the Innovative Marine Minimax Pro Series Media Reactor. It has an impressive volume capacity of 150 milliliters, which is enough for most medium-sized tanks.

Another benefit of this device is its impressive build quality. The entirety of the body is made out of high-quality cell cast acrylic that can withstand most drops and bumps without issue. Moreover, it also comes with an attachment bracket that makes it much easier to attach to your tank. All you have to do is hook on the bracket and slide it onto the edge of your tank for a secure fit.

While the build quality may be fine, one issue that many reactors face is leakage through the top and connections. Thankfully, Innovative Marine has worked around this issue with their redesigned rubber cap that creates a tight seal at the top of the reactor. In other words, there are minimal chances of any leaks once you have it sealed.

This device will also save you money on external purchases as it comes with a 10 to 52 GPH pump and tubing right out of the box. The pump provides a decent flow rate and has responsive controls, making it easy to use. Additionally, it is quite energy-efficient, so you will also end up saving money on your electricity bill.

The only thing we did notice is that the filter media did occasionally clog. While this wasn’t as much of an issue with GFO, if you plan on using other types of media as well, you should be mindful of it.

Check price button

– Overview

If you are a beginner aquarist looking to buy your first GFO reactor, the Innovative Marine Minimax Pro Series Media Reactor is one to look into. It comes with simplified instructions that make setup and usage very easy. Even though it has a compact form factor, it provides an impressive media capacity that can keep your tank clean of algae without taking up too much space.

5. AQUATOP MR-20 Multimedia Reactor

– Pros

  • Pump and tubing included
  • Simple installation
  • Easy maintenance
  • Up-flow filtration for improved efficiency

– Cons

  • Not very powerful

If you have a high bio-load reef tank and are looking for a GFO reactor to keep algae-free, the AQUATOP MR-20 Multimedia Reactor can be an excellent pick. It offers a powerful up-flow filtration system that increases filter media efficiency so that you can get the most out of your GFO media. Also, with a high-quality acrylic build, you won’t have to worry about breaking this reactor under pressure.

The reactor is rated for tanks up to 75 gallons, and we found that it works perfectly around the 70 to 80 gallon range. Apart from that, it is decently sized with a height of 15 inches and easily fits into most medium-sized aquarium setups. That being said, if you have a smaller setup, it can be a bit too much for cramped spaces.

Once you have the filter set up, it is pretty intuitive and simple to use. The package comes with  Aquatop’s SWP-230 water pump and sediment discharge filter with adjustable flow. This efficient pump makes the reactor much easier to use in all kinds of tanks, as the flow rate can be adjusted according to your requirements. Moreover, it also comes with intake and output tubing, so you’ll have everything needed to get it started right away.

An added benefit of the AQUATOP MR-20 Multimedia Reactor is its easy-to-remove lid. It makes maintenance or filter media changes much easier and cleaner as compared to many other options in the market.

Check price button

– Overview

The AQUATOP MR-20 Multimedia Reactor is a powerful and small device that can keep your tank clear of algae without any issues. It uses a unique up-flow filtration system that increases water-to-media contact time, which in turn improves the overall cleaning capacity of the device. Apart from this, it also comes with a pump and all the necessary tubing to get it set up right away.

Buying Guide

Here’s a list of some things you should consider when looking for a phosphate media reactor:

– Capacity

When looking for a new GFO reactor, knowing what capacity you need is important. That is because the capacity for media is the amount of granular ferric oxide you can use, and it will also decide how much water can be filtered.

So, if you have a smaller tank that is around 50 gallons in capacity, a GFO reactor with a smaller capacity will do fine. That is because you won’t be filtering as much water, and the minimal amount of GFO can clean the tank just well. That being said, for larger tanks, you will have to look for reactors that can carry more media to filter through large amounts of water continuously.

– Build Quality

When you are using a GFO reactor or any similar type of device, any leaks or cracks can be harmful. That’s because the device often contains harmful chemicals and substances that can be fatal for your pets and the aquatic environment. Due to this, looking for a GFO reactor with good build quality is important, especially if you are keeping it at a height.

Some of the better options in the market come with cast acrylic, which is known to be impact resistant up to a certain degree. Moreover, it can also withstand water pressure making it an excellent choice for most tanks. So, make sure to keep in mind the overall build quality and materials used before deciding on your GFO reactor.


Let’s discuss a few frequently asked questions related to GFO reactors:

1. What is the purpose of a media reactor?

A media reactor is responsible for cleaning your tank water by passing it through filter media. It could be any kind of media depending on the type of filtration you need, such as GFO for inhibiting algae growth. The reactor works by forcing water through the media and increasing contact time for optimal filtration.

2. Does GFO remove nitrate?

No, Granular Ferric Oxide(GFO) reactors work by removing phosphates from your tank, which are responsible for algae growth. While this might reduce nitrate density, it will not remove nitrate from your tanks. So, you will have to use other kinds of filters for nitrates.

3. How long does GFO last in a reactor?

The Granular Ferric Oxide in your reactor will last anywhere between four and eight weeks. That depends on the bioload of your tank and the water flow rate for the reactor itself. Also, elevated phosphate levels will contribute to your GFO needing to be replaced sooner.

4. Can you use too much GFO?

Yes, you can use too much Granular Ferric Oxide in your tank. While GFO is essential for removing phosphates from your tank and keeping it algae-free, too much can also be harmful. That is because some amount of phosphates is necessary for the growth of the coral and plants in your reef tank. So, make sure you monitor the Po4 levels in your tank and don’t overuse GFO in your tank.

5. Do biopellets reduce phosphates?

Yes, biopellets do reduce phosphates but in very minimal quantities. Biopellets work by providing a home for the cultivation of beneficial bacteria, which in turn filter your tank’s water. These bacteria are highly efficient at removing nitrate from your tank but, along with this, also consume minimal amounts of phosphate. So, while it is pretty tiny, bio pellets will reduce the phosphate levels in your tank.

6. Should I run GFO all the time?

No, unless the phosphate levels in your tank are high, you shouldn’t run GFO in your tank. Overusing GFO can lead to nutrient level instability and also reduce the phosphate levels in your tank too much. So, the best thing you can do is regularly monitor the phosphate level in your tank and use your GFO reactor when needed.

7. When should I change my biopellets?

Best gfo reactorBiopellets should be changed every six to twelve months, depending on the overall bioload in your tank. For example, if you are using a large amount of media in a relatively small tank with minimal animals and plants, you can probably change the bio pellets yearly. On the other hand, for higher bio load tanks with more plants and fish, every six months is a safe guideline.


After thorough testing of all the options on this list, we have come to the conclusion that the Two Little Fishies Phosban Filter Media Reactor is the best overall GFO reactor. This media reactor offers you powerful filtration capacity while still being priced reasonably. So, you can buy this even if you are on a tight budget and keep your tank algae-free.

Apart from this, the carbon and GFO reactor is designed for use in tanks as large as 150 gallons in capacity. While this is quite impressive, if you have a larger tank, you can efficiently utilize multiple reactors together with GFO media to keep your tank clean.

That being said, each reactor on this list has its advantages and might be a better option for you. So, we hope this list helps you find the perfect choice for your setup.

5/5 - (15 votes)


Please enter your comment!
Please enter your name here