7 Best RO/DI Filter System for Aquariums

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Is your faucet water way too polluted for your fish? Ever thought of purchasing a RO/DI system for your aquarium? Stick around and see the best systems you can buy and what exactly a RO/DI system does.

Best Reverse Osmosis System for Aquariums

Below you can find the best RO / DI systems we consider most suitable for aquariums:

1. AquaFX Barracuda RO/DI Aquarium Filter

It is considered to be one of the most efficient RO/DI systems. You can use it for both saltwater and freshwater aquariums.

The AquaFX Barracuda is a four-stage filtration unit. One of its best features is that it comes with two carbon filters, to ensure that the water coming out is completely transparent, odourless and tasteless. This feature makes it one of the strongest filtration units.

The AquaFX Barracuda usually works with ¼” hose tubing. The entire system weighs 12 pounds and produces one hundred gallons per day. These features make the AquaFX Barracuda very attractive.


  • It has a stronger and faster water flow, compared to other filtration systems.
  • The filtration and purification processes are perfect, thanks to the two carbon filters and its strong TFC membrane.
  • The installation of the system is very easy. It does not take much time to set up everything and connect the system to the water supply.
  • The components have a large lifespan, so you do not have to worry about replacing them anytime soon.
  • The TDS meter gives a zero reading for a long period of time. The system remains efficient for a long time before it would need a replacement.


  • The waste to filtered water ratio is slightly higher than other models. It produces a lot of waste water. Thus, the water bill can be pretty high
  • It is relatively heavier than other systems. So, once it has been set up, it will be difficult to move it or change the settings.


2. Aquatic Life RO Buddie System

The Aquatic RO Buddie is a three-stage filtration unit with three different types of cartridges to filter and purify water. And there is another model that has four stages, enabling further purification of water. The two models have capacities of fifty and one hundred gallons per day, respectively.

What makes this unit even more special is the filtered/waste water ratio. The average waste to filtered water ratio is 4 to 1. The Aquatic RO Buddie weighs 3.1 pounds.


  • The Aquatic RO Buddie is that the filtration process is absolute and perfect for any type of water.
  • It is perfectly safe for human use. The Aquatic RO Buddie produces colorless, odourless and tasteless water; making it available for human consumption.
  • Its greatest feature is its compact size. You will not need to rearrange the place or make room for the Aquatic RO Buddie. It is designed to be very small so that it can perfectly fit in even the tightest spaces, such as cabinets.
  • The cartridges have a long lifespan. Each filter has a lifespan of six months and can perfectly work for producing about 1500 gallons of RO/DI water.
  • The replacing process is nothing to sweat about. Just twist the top off, remove the used membrane, insert the new one and reattach the top.
  • Regarding the additional fourth stage, which is the deionization filter, you can easily know when it needs replacement. The color of the filter changes.


  • The system does not arrive with the needed tubing in the package. You would have to purchase the tubing on its own.
  • Although the Aquatic RO Buddie is affordable as an entire system, the replacements for the cartridges can cost up to the price of the entire system. The cost of the entire system is mostly the cartridges.
  • Unlike other devices that can be embedded in the aquarium, the Aquatic RO Buddie is placed and used outside the aquarium. You have to filter and purify the water first before adding it into the tank. Whenever you want to change the water inside the aquarium, you have to transport the water to the system.
  • New York has relatively higher water sediment than anywhere else. So, in order for the citizens of the Big Apple to have the same level of water purification, they have to purchase a pre-filtration stage separate from the three-stage or four-stage system. Therefore, it would cost them a little bit of extra cash.


3. Koolermax AR-122 RO/DI System

It is one of the best-selling reverse osmosis and water deionization systems. What makes the Koolermax AR-122 special is the fact that it is a six-stage filtration unit. It has a powerful sediment filter, two carbon filters to eliminate the existence of chlorine, a membrane that removes almost 80% of the undesired impurities and two deionization filters.

The ultra-purification process along the six stages guarantees extremely safe water. Since the system has more than the usual number of stages, it is a little heavier.

The Koolermax AR-122 weighs 17 pounds. What sets the Koolermax AR-122 on another level is that it is one of the rare systems who have a capacity of 120 gallons per day.


  • A fast and strong water flow. The filtration process is fast.
  • A low waste to filtered water ratio. This is considered to be one of its best features, compared to other RO/DI systems.
  • The additional (second) deionization filter ensures the elimination of any heavy metal ions or electrolytes present in the water
  • The installation of the system is very easy and the instruction manual is very helpful


  • It does not work for all types of water. Water types with high TDS may not be completely purified.


4. LiquaGen 5-Stage RO/DI System

The manufacturing company claims that this RO/DI purification systems are not only used for aquariums. It can be used in laboratories or any other place that needs ultra-purified water, as the company claims that the LiquaGen produces zero ppm water.

The LiquaGen is a five-stage filtration system. It has a high rejection membrane to trap all the undesired impurities. The LiquaGen produces water that is safe for human use. It weighs 14.55 pounds and has a capacity of 75 gallons per day.


  • The company provides a warranty of 2 years with complete customer support. Most of the other companies have a warranty of only one year.
  • The greatest thing about the LiquaGen is that it comes pre-assembled. You only need to connect it to the water supply. Thus, the setting process is a no brainer.
  • The LiquaGen works in other places besides aquariums
  • The membrane is more powerful than the ones found in some other filtration systems.


  • At first, the system may not be 100% efficient. It takes a little bit of time for the LiquaGen to work with its best potential.
  • The LiquaGen does not fully filter and purify water types with TDS higher than 350.
  • Some people find that it costs way too much and does not offer the expected services.


5. Geekpure 3-Stage Aquarium Reverse Osmosis System

The Geekpure RO3 is a three-stage reverse osmosis unit. With its compact size, it is portable and easy to fit. The system includes a sediment filter, a carbon filter and a TFC membrane; basically, the basic components of a reverse osmosis system.

The Geekpure weighs about 4 pounds and has a capacity of one hundred gallons per day. It is relatively cheaper than many other filtration units.

The Geekpure works efficiently at a water temperature of 40 Fahrenheit to 105 Fahrenheit, and a pressure of 40 PSI to 100 PSI.


  • It’s one of the rare portable water purification units.
  • It can work with water types with high TDS.
  • The Geekpure produces water that is suitable for human use.
  • An ad-on drinking water kit with a tank of 2.8 gallons capacity.


  • The unit does not have a deionization filter. So, the chance of having electrolytes and heavy ions in the water is present. Most people go for the five-stage system.
  • Despite that instruction manual is very straightforward, the installation and setting process is not easy and takes quite an amount of time.


6. AWI Typhoon 5-Stage RO/DI System

The AWI Typhoon is a five-stage RO/DI filtration system. It features two carbon filters to guarantee the complete elimination of chlorine. It comes with a powerful FilmTec membrane.

The entire package weighs about 22 pounds. It is very easy to install, as the system is pre-assembled. You only need to connect the system to the water supply. It has a capacity of 75 gallons per day.


  • Both carbon filters are micron acid washed and work with the same efficiency.
  • The package provides all the tools you will need for installing the system
  • Fast water flow and fast installation


  • The waste to filtered water ratio is relatively high, compared to other RO/DI systems.
  • It is heavier than some other five-stage filtration units.


7. Premier 5-Stage RO/DI Water Filter System

The Premier filtration system is claimed to be excellent for aquariums, laboratories and other places that need ultra-purified water. The greatest feature of the system is its great capacity of 150 gallons per day.

The filtration unit is pre-assembled to make the installation process smooth. The Premier system comes with two carbon filters to achieve the complete elimination of chlorine. Also, it has a deionization filter, used for trapping any escaping ions or electrolytes.

It comes with two white housings and one clear housing pre-filter.


  • The installation process is very simple. You can find everything perfectly explained on the instruction manual.
  • The package comes with all that you need.
  • It has a huge capacity, placing it in its own class.


  • The Premier system is only suitable for city water. Water types with TDS higher than 350 will not come out perfectly pure.
  • Some people have complained about the difficulty in finding replacing parts.


How does a RO/DI System Work?

How does a RO/DI System Work?

How does a RO/DI System Work?

The total dissolved solids (TDS) are the main key to deduce if the water is suitable for reef tank use. By using a TDS meter, you can know the ability of water to conduct electricity. If the reading of the TDS meter is zero, then the water is perfectly safe and the purification process was a complete success. If not, one or more of the filters of the stages need replacements.

Some tests, such as total dissolved solids after both reverse osmosis and deionization stages and filtered to waste water ratio are perfect judges on the reverse osmosis, deionization and filtration processes. You can find out the quality of the RO/DI water by conducting these tests.

The Aquatic RO Buddie produces pure freshwater that you can use as a habitat for fish. But the produced water is not suitable for coral reefs. You can conduct a simple experiment to judge the efficiency of the filtration system. Just get a timer or a stopwatch and see how long it will take for the unit to produce one gallon of RO/DI water.

The basic components of a water filtering unit are the following: a sediment filter, a RO membrane, an active carbon filter and a mixed bed deionization cartridge. To achieve the optimum pure water, all these components must be present in the unit, as each one plays a different role in the process.

When you look at it, water seems transparent, odourless and tasteless. But, is it perfectly safe for use? How can you be sure that the faucet water doesn’t have any bacteria or microbes or undesired minerals? Let’s face the fact that a good filtration process is necessary.

The most important thing about a RO/DI unit is the Thin-Film Composite (TFC) membrane. It is a semi-permeable membrane, found in the center canister to remove the undesired materials, such as dissolved minerals from the water. Basically, the TFC membrane is the core essence of the reverse osmosis process.

The system must also be accompanied by a sediment filter. The main function of the sediment filter is to remove the bulky materials that can act as an obstacle to the reverse osmosis process. Also, there is a carbon filter that works on removing the bad taste and odor from the water.

You achieve perfectly clear, odourless and tasteless water because the carbon filter removes harmful metal ions and chlorine. Water must pass through the sediment and carbon filters first before passing through the TFC membrane, because it is a thin membrane that can be destroyed if subjected to heavy or bulky solids.

The exiting water from the three main stages of any good RO/DI system is perfectly pure and safe for use. However, there is a chance that some ions may pass through the three stages. It is not a perfect world after all. For this reason, an additional filtration stage was created.

The fourth stage includes a deionization color changing mixed bed resin cartridge. It includes both cations and anions, allowing it to attract the escaping ions and form salts that cannot pass through the filter at all. Sadly, this particular stage needs regular replacing, as the present cations and anions are continuously being used up.

How to Choose a RO/DI System for Your Aquarium?

Basically, you need to check the space you have for placing the system. Also, you have to check your water quality using the TDS test, in order to find out if you would need more than a four-stage system.

Benefits of using a RO/DI System for Your Aquarium

Water is the only habitat for fish and let’s face it, pure water is hard to obtain from your faucet.

The RO/DI system manages to eliminate most (if not all) of the undesired and harmful materials found in the water. Thus, you’ll be ensuring a safe and perfect environment for your fish.

How Often Should you Change a RO/DI Membrane?

RO/DI Membrane

RO/DI Membrane

Generally, for most of the RO/DI, you should replace both the sediment and carbon filters every six to twelve months. As for the TFC membrane, its replacement should take place every two years.

These are the estimated times for changing the RO/DI system’s components. If the manual specifies the exact replacing times, you should commit to them.


In the end, we hope that this list was helpful, and that you understood the concept of reverse osmosis systems.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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