The Best RO/DI Systems For Reef Tanks 2022 – In-Depth Reviews

1. AquaFX Barracuda 2. Aquatic Life 3. LiquaGen


Aquarium keeping is a rewarding and interesting hobby. Those who enjoy taking care of aquariums, reefs or tanks know that there are many specific little jobs to do in order to keep the fish and marine life happy- and, in a way, that is part of the appeal.

So much of the time spent in keeping the aquarium healthy and blooming is actually spent in keeping the water healthy and clean. It’s almost like the water is our pet! In nature, the biggest threat to animal life is water pollution. Luckily that can be easily avoided on your aquarium with the best ro di system for reef tank available.


It may come as a surprise for many that tap water is not safe to use in reef aquariums. While, in many places, tap water is not safe to drink, we will not die if we take a sip of it. That is not the case for delicate organisms such as corals, and they may perish if they come in contact with the most common contaminants found in tap water (even treated tap water).

It is not necessary, though, to buy gallons of pure, filtered water to last for years. With the best reverse osmosis system for aquarium, you can achieve amazing results. This simple and affordable device can filter almost 100% of dangerous tap water contaminants and metals.

What Exactly Is An RO/DI System And Why Do I Need It?

RO stands for Reverse Osmosis, as you probably know from science classes. Osmosis is the natural phenomenon of water going spontaneously from a solution with a low concentration of salts to a solution with a high concentration of salts, through a semipermeable membrane. Reverse Osmosis is, well, the opposite of that.

In the reverse process, the heavily concentrated water is forced with high pressure through a membrane – which acts as a filter, cleansing the water and getting rid of many of those contaminants we talked about before, around 85% to 95%.

To complete the process, the Deionising Vessel, the DI, filters the remaining harmful particles. You may have heard of this device as it can also be used as a stand-alone machine to filter drinking water and goes by other names, such as DI Filter, Ion Exchange Filter or Resin Filter. We will go into more detail about how this filter works on the next section.

Saltwater aquariums and reef tanks require an equipment that filters the water and converts to an acceptable level. Corals and more delicate fish are very sensitive to the additives in tap water. Tap water can also encourage some damaging kind of algae to grow in your aquarium.

That said, there are three ways of getting safe, reliable water into your tank:

Getting natural water from the ocean

It is possible to get water directly from the sea and using it for your aquarium. Although that may seem like a reasonable idea, it is not feasible for everybody; you may live far from the sea or don’t want to make the trip every time you need to change the water. It is not a practical solution.

Buying water from a pet store

Good pet shops have big and efficient equipment to make safe, clean saltwater. The cost, however, can add up if you are constantly buying water in bulk. It can be very difficult to transport as well.

Making the saltwater yourself

The answer for many aquarium enthusiasts is to take the task to make water to themselves. It may seem daunting, but it is the most cost-efficient in the long term. With the help of the information we put together, you will be able to use tap water to make fresh, clean and risk-free saltwater for your reef.

Do The RO System And The DI System Always Come Together?

No, they don’t. You can purchase both of them separately or get a device that combines them, based on your needs or tank specifications. Even though that may seem complicated, we elaborated a comprehensive but straightforward guide to the best RO/DI systems for reef tanks.

How Do The Best Reverse Osmosis Systems For Aquarium Work?

Usually, the best RO systems work in three, four, five or even six stages. Even though you do not need a diploma in Chemistry to own an aquarium, it is always good to understand the processes that are happening in the environment your fish lives in.

What’s more, if you comprehend the steps and reactions of the RO/DI system, you can maintain it better, invest in quality parts and kits and save money in the long run. These are the basic phases of filtration:

1. Sediment Filter

The first part of the process is the sediment filter or a prefilter. Its main purpose is to protect the osmosis membrane (the most important piece) so that it collects large particles of sand or other sediments.

2. Carbon Filter

Another prefilter, this one removes chemicals that could contaminate the membrane – such as chlorine (very common in tap water).

3. RO Membrane

The most important and expensive fragment of the equipment is the Reverse Osmosis Membrane. It comes with a pressurizer that pushes water to less concentrated solutions, filtering out both organic and inorganic elements. They can be fluoride, copper, arsenic, lead and several more.

4. DI System

The DI or Deionization Filter, in theory, performs the same role as the RO, which is to filter the water and make it purer. It does that, however, using a different process. The resin in the DI comes with hydrogen molecules.

The system attracts the remaining minerals of the water- the ones the membrane couldn’t filter, and it exchanges the chemical molecules for the hydrogen molecules, leaving the water crisp and clean. When the DI “runs out” of hydrogen molecules it is time to replace it.

Some RO filters add a second carbon filter to further protect the membrane. That makes sense; the better the membrane, the cleaner the water.

Some also have another filter added after the membrane, with the purpose to “polish” the water that comes through the membrane, removing any odour or taste the osmosis process may leave. These can account for stages 5 and 6 on a filter.

Factors To Look For When Buying the Best RO/DI System For Reef Tank

There are some aspects to watch out for when trying to find the best RO/DI system for reef tanks. It is important to check each specification against the type of aquarium, fish and corals you have, so you can end up with the perfect match for your ecosystem. Some of the things to look for are:

1. Number Of Stages

An RO system has to have at least three stages. Anything less than that can compromise the quality of the machine since the membrane is not protected enough. Ideally, you want a device with four stages: two pre-filters to protect the membrane, the membrane itself and the DI portion.

However, if you have organisms in your aquarium that benefit from a pristine, super filtered water, you may want to invest in a system with five or six stages. Analyze the needs of your reef when thinking about the number of stages.

2. What Exactly Each Stage Contains

It is crucial to understand what each stage stands for in the system in question. It is of no use if a piece of equipment claims to have five stages, but two of them are essentially the same. If a system has six stages, the location of the filters matter as well- you want one sediment filter and two carbon filters before the membrane stage.

After all, the whole point of adding these steps is to protect the membrane. Some systems add an extra carbon filter after the membrane to polish the water, and that is okay, as long as there are enough steps before.

3. Capacity

The capacity of RO/DI systems is measured in Gallons per Day (GPD). It is crucial to choose that feature based on the size of your tank. Because, if an RO system can only handle an X amount of gallons per day and your aquarium needs more than that, you may need to connect another tank of water separately to have a spare supply.

To calculate the GPD you need, divide the size gallons in your tank by the interval of days you change the water. For example, if your tank has 20 gallons and you change the water every 5 days, you need an RO/DI system of a 4 GPD.

4. Quality Of Parts – Especially Membrane

The membrane is the backbone of the reverse osmosis system. It is crucial that it is made from a quality, durable material. A high removal membrane can filter up to 95% of contaminants in water, and that is the main reason to get an RO system. Since the membrane needs to be semipermeable, it can be very sensitive. When quality filters are added before the membrane stage, they will protect the membrane against big particles and dangerous chemicals. That will make sure the membrane lasts for a long time.

To make it even easier for you, we found the top 8 best RO/DI systems for reef tank that are available on the market. Any of these choices will make for a great filter – but keep reading to find the perfect fit for your aquarium type.

Top 8 Best RO DI Systems For Reef Tank In 2022

1. AquaFX Barracuda RO/DI Aquarium Filter

AquaFX Barracuda best ro di system for reef tankThe Barracuda is a very popular choice among saltwater aquarium keepers and a seriously solid option for your filtering needs. To start with, AquaFX is a well-established brand on the reef business. It serves enormous customers, like universities and, I’m not joking, NASA.

With engineers and specialists on their team, this is a company more serious aquarium owners certainly trust; they developed a good amount of new technology that they use in their system.

Lucky for the aquarium hobbyists, AquaFX holds a very affordable RO/DI system perfect for home needs. You can choose between the 50 and 100 GPD ones, based on the size of your tank. It is a neat four stages filter with two chlorine carbon filters that protect the membrane and assures for effective filtration. It also includes the Deionization section – which really makes for a complete filtration procedure.

Another advantage that this RO/DI system has, when compared to others, is the fact that all its pieces are made in the USA, which makes it easier for the company to guarantee their quality. It is easy to install and use, and customers have reported that it continues to perform well after many months.

It is a fast machine, and it fills up a five-gallon bucket of water in under two hours. That is possible because it comes with a pressure gauge that makes sure water is going through the filters and membranes at great speed.

All reverse osmosis systems are expected to produce wastewater in the process, and the Barracuda is no exception. Since is such an efficient system that produces water with a 0 ppm (parts per million) percentage of impurities, it does waste a bit more water than other models.

Reviews also show that the instructions can be a little complicated, but certainly not impossible to read. It is also slightly more expensive than similar models, but the quality that it offers is unmatchable.


  • Fast process with great pressure
  • Efficient filtration with amazing results
  • American-made with quality parts


  • High water waste
  • Manual a little complicated
  • Higher price

2. Aquatic Life RO Buddie Reverse Osmosis Systems

Aquatic Life RO Buddie Reverse Osmosis SystemsThe Aquatic Life RO System is a very practical, easy option to consider. It comes with a faucet adapter that makes set up a breeze.

It is incredibly affordable, so if you love fishkeeping but can’t justify spending all your spare money on more fancy brands, this is a great alternative.

It has three stages of filtration- the two, very important, pre-filters and the RO membrane. You can choose between 50 or 100 GPD and you can replace all pieces effortlessly. If you are a beginner aquarist, I’m sure this all sounds very appealing.

Another allure of the Aquatic Life filter is that it is compact. When you live in an apartment or if you do not like clutter and bulky appliances, this reverse osmosis system is perfect for you. It is discrete and easily installed and uninstalled – a great companion if you move a lot. The whole process of manual reading, installing and getting the first litres of water clean takes less than an hour.

It is important to note that the number of gallons per day advertised for most systems is the total number; that means both clean water and filtered water. That can surprise many customers, but actually that number is still a generous, enough amount that is worth in the long term. With a 50 GPD model, you produce about 15 GPD of usable water. An amazing number, making this one of the best systems under $100 available.

Users have reported having used original parts for up to a year before needing replacements, and even then, replacing parts were cheap and durable. If you are starting out or if you like the sound of an effective, small three stages RO system, this model is for you.


  • Affordable
  • Easy to set up
  • Small and compact


  • Only three stages

3. LiquaGen: 5-Stage Reverse Osmosis and Deionization RO/DI

LiquaGen 5-Stage Reverse Osmosis and Deionization RO DIThe LiquaGen is a more complex, five staged RO system with DI included. It promises to deliver water as clean as 0 ppm (0 contaminants parts per million), and it delivers on that promise using two carbon filters to remove chlorine and a high-quality, US-made, membrane.

Set up with this system is practically non-existent. Apart from the tubes to bring water in and out, the machine arrives in your house completely assembled.

That is perfect for beginners or anyone who does not enjoy putting together fiddly, complicated little pieces of equipment. It is not as fast as other models, filters water a fewer rate than other similar models. That makes it more suitable for small and medium tanks.

LiquaGen is reported to have one of the best customer services regarding RO/DI systems, and any problems are quickly solved, either with information or even new pieces. It is one of the best RO/DI systems for reef tank at this price range, with its many filtration stages working properly and resulting in safe, soft water for fish and coral. It is not as compact as the AquaticLife, but if you have space, it is a smart choice.


  • Great value for money
  • 5 stages of filtering including DI
  • Easy to assemble


  • Not as fast as other models
  • Big size

4. NU Aqua Platinum Series Deluxe – 5 Stage RO

NU Aqua Platinum Series Deluxe - 5 Stage ROWith a capacity of 100 GPD, the NU Aqua Platinum system comes with a five-stage process that promises to stand out among all others. Let’s take a look at the process.

The first step is the traditional sediment filter that rids the water of particles and sand, followed by two carbon filters to prepare the water to go through the membrane.

After the osmosis part, the water goes through yet another carbon filter (made with coconut shell) that polishes the water and makes it odourless and tasteless.

It is one of the only RO systems that comes with a DVD that walks you step-by-step through the installation, making it clear to assemble. It doesn’t leak and is overall a trustworthy source of filtered water.

The first filtration container is transparent and that makes the design more stylish and pleasing than others. It also means it is easier to visualize when parts need changing. Some people had problems with leaking parts, though, and we should be extra careful when installing.


  • Stylish design
  • Five stages of filtering


  • No DI included
  • A few people reported leaking

5. Koolermax AR-122 6-Stage RO+DI Aquarium Reef RO System

Koolermax AR-122 6-Stage RO+DI Aquarium Reef RO SystemKoolermax has an impressive six-stage filtration system ideal for those who are particular about their aquarium water and want a lot of filtration stages at an affordable price.

It comes with all the components you need, and the pressure gauge even shows you when you need to replace the bottom three filters.

Even the best RO/DI systems for reef tank don’t have a capacity as high as the Koolermax, that can filter an impressive amount of 120 gallons per day.

Owning a big saltwater aquarium can be a challenge, but this system is definitely up for it. The parts and filters are all tested for quality and need replacing only once a year.

Some customers had problems with its setup since the instructions can be a bit unclear. When is time to change the filters, you are better off buying them with Koolermax themselves because their size is somewhat specific. Since they last for such a long time though, that is not really a huge problem.

The biggest selling point of this system is certainly the number of stages the water goes through, so let’s quickly break them down. The first three filters are the pre ones – one sediment and two carbons. After that, the liquid passes through the (high-quality) membrane and finalizes by undergoing two DI treatments. It really is amazing the number of steps this system has for under $150.


  • Six stages of filtering
  • Two DI steps
  • Great value for money


  • Installing can be a bit fidgety
  • Their own filters are the ones that fit the best

6. SpectraPure MaxCap RO/DI System

SpectraPure MaxCap RO DI SystemIn some places, purified water for saltwater aquariums can cost $1 per gallon or more. As we are, ideally, constantly changing the water in our tanks, it just makes sense to buy an RO system.

The SpectraPure is one of the best ones you can find for its price range and a solid reliable choice. It comes with a DI stage as part of it, and that really makes a difference

The SpectraPure is another filter with five stages of filtration. One sediment, one carbon, one membrane and two DI ones.

It is always a pleasant surprise when a system comes with not only one, but two deionization stages because, since this is a process that works by exchanging contaminant particles chemically, it is extremely productive.

It is pricier than most, but if that is not a worry, why not invest in a quality product that will definitely give the expected results? Many seasoned aquarists and professional shops go for this model, and we can see why.


  • Premium model
  • RO + DI
  • Guaranteed results


  • Price

7. 0PPM Portable 150 GPD Reverse Osmosis RO+DI Filtration

0PPM Portable 150 GPD Reverse Osmosis RO+DI FiltrationThis Reverse Osmosis system is complete with a DI step and works great for getting the water at 0 parts per million level. If you need a budget choice that still gets the job done, you would be wise to consider this one.

Leaking is one of the major problems with cheaper filtering systems. If your system is losing half the water between the faucet and the filters, that means you are wasting and spending way more than anticipated. This RO/DI, if installed properly, does not cause this type of worries.

Users have reported that it is difficult to find replacement filters for the ones that come with the package. It is also slower than other designs, so it only works better for small tanks.


  • Reliable budget option
  • Included DI stage


  • Replacement filters are difficult to find
  • Slower than others

8. Puroflo 5pc RO Water Filter Replacement Set

Puroflo 5pc RO Water Filter Replacement SetYou may feel nervous when you realize your system is malfunctioning and the filters look dirty and used. The solution is easy though, and no professionals are needed.

The Puroflo replacement set comes with all the filters necessary for when the filters require changing. The installation is so simple that even a child can do it (with the supervision of adults of course!).

It comes with two carbon filters, one sediment filter, one membrane and one in-line carbon. Set up takes about one hour and it works as advertised.

It is possible to buy components separately to try and build the best RO/DI system for reef tank, but it is not really worth the effort. Kits like this one come with all the right parts to give you and your fish the best possible experience.


  • Good for the price
  • Simple


  • No DI included

5 Ways To Use Up Wastage From RO Systems

As we pointed out before, all RO systems produce filtered water and “waste” water – the one that can’t be put into the tank. Many people feel guilty about all this wastage, so we came up with a few ways you can put that water to good use:

1. Wash Your Dishes

If you can find a way to collect the water from the RO system, you can store it for washing your cutlery and dishes. That action does not require any special type of water, so you can use any wastage water with any worries.

2. Wash Your Car

Car washing can be one of the biggest sources of wasted water- a standard hose uses up to 100 gallons of water in just ten minutes. If you stash RO wastewater to use it when washing your car, you can save double the amount of water and money.

3. Use It In The Washing Machine (Careful With Delicate Clothing)

Redirecting the waste towards the washing machine is also a great use for RO waste. A standard washing machine can use 30 gallons of water per load, and if you use the seized reverse osmosis water, you will be saving a considerable amount of water per week.

Be careful and test it before with delicate clothing, since results can vary when the fabric is very fragile.

4. Clean Toilets

Toilet cleaning is one of those activities that really do not require any kind of filtered or special water to do it. Use buckets of it with no worries.

5. Wash Floors – And Virtually Anything

Scrub floors, walls, use it for furniture cleaning, fill up your dishwater and much more. If you can wash it – you should wash it with RO wastewater.

It is important to remember that RO water, even wasted, does not have many minerals, salts and characteristics that tap and shower water contain. Therefore, if you want to use it to water your plants or wash your hair, test it first for a couple of weeks and follow the results closely – as it can damage your hair or plants.


As we could see from this comprehensive list, it is not that hard to choose the best RO/DI system for your reef tank. It is all about research and picking the one that matches your saltwater aquarium the most. Try to invest in the best quality one you can afford, as saltwater organisms can be very sensitive.

Reverse osmosis systems, preferably with a Deionizer stage included, are really a necessity for aquarium hobbyists. Setting up a tank is hard work, and nobody wants to see that hard work wasted because of bad water.

Besides, it is all about maintaining a happy and healthy aquamarine life- and now you know exactly how to do that. Never buy any item without properly comparing models before, and that is extra valid when dealing with live beings.