If you’ve set up your reef aquarium, you’re probably smitten by its aesthetics. Well, it is our painful duty to inform you that if you want this beauty to last, you’ll need an RO/DI (reverse osmosis) system.

(But I’ve already spent a considerable amount on my aquarium!!)

We understand.

Saltwater tanks are costlier than their counterparts. Furthermore, if you want your gorgeous corals, invertebrates, and fishes to survive, then you need clean water.

The RO DI system can ensure water free from any impurities. Even the slightest of contaminants can pose a massive threat to the tank inhabitants. Thus, you’ll need a water filtration process capable enough to provide pollutant-free, clean water.

In this article, we aim to provide a comprehensive breakdown of the best RO/DI system for reef tanks.

You’ll find all the pertinent information (what’s and why’s) recommendations, and even a guide to choosing the perfect product for your aquarium.

Without further ado, let’s hop in.

But first, take a look at our top 3 picks –

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The RO/DI system (What and Why):


In brief, it’s a filtration mechanism that removes impurities usually carried by tap water. The technology of this system boomed significantly, having the ability to eliminate nearly 99% of pollutants (impressive!).

The reason you need an RO/DI is because the tap water one receives from either lake or centralized water plants are highly unreliable. They contain several contaminants that can significantly alter the natural ecosystem of a reef tank.

Let’s look at the list:

Hard Alkaline:

Depending on the geography of your area, tap water may contain magnesium carbonate or calcium in high quantities. They might liquefy, creating hard alkaline water, and if you use them in your aquarium, damage the inhabitants.


Water refinement plants must ensure that the water consumed is safe. Thus, they no option but to use disinfectants. Chemicals such as chlorine and chloramine are healthy for humans but can have a detrimental effect on reef tank inhabitants.

Nitrate and Phosphate:

Your tap water may have an abundant supply of nitrates due to farming lands nearby. Moreover, to prevent water pipes from corroding treatment, plants add phosphate as a preventive measure.

The umbrella term for all the elements mentioned above is TDS (Total Dissolved Solids). Any of these chemicals can have a detrimental effect on the reef aquarium ecosystem.

Hence, the RO/DI system serves as the guardian angel, the wholesome protector eliminating TDS and ensuring a safe and healthy environment for your fishes, corals, and inverts.

Best Rodi System For Aquarium

Reviews of Best Reverse Osmosis Systems for Aquarium And Reef Tank

Here is a list of our top picks. You’ll find a comprehensive breakdown with the pros and cons outlined for your better understanding. Let’s take a look.

1. AquaFX Barracuda RO/DI 100 GPD Aquarium Filter

The RO DI, better known as the reverse osmosis water system, is usually used in a kitchen for decontaminating the water that we drink. But most people aren’t aware that it is also applicable to an aquarium.

So not only can it keep you safe from the impurities found in tap water, but it can also keep your fishes healthy and lively. The AquaFX RO/DI Aquarium Filter is one such equipment to fulfill your filtering commitment.

Luckily for you, the filter comes at a very affordable price, which is ideal for domestic users. This model comes with many components that will enable you to purify the water successfully.

The system weighs around 12 pounds. Its filter can pass 100 gallons of water per day, which is, compared to other models, quite a lot. This model has three separate filters which are great because it completely wipes out contaminants from your tap water.

The unit has four stages of filtration and has two chlorine carbon filtrates. This will shield the membrane from toxins and ensure efficient filtration. Another excellent feature is the deionization section, which effectively seals the whole filtration process.

To set it up, you will have a shut-off valve, a filter wrench, and connect fittings. You can also select a feed adapter according to your preference. The zero rust metal filters ensure high durability.


  • Filters 100 gallons of water every day
  • No rust metal filters
  • Contains pressure gauge


  • Complicated manual

2. SpectraPure Reverse Osmosis System

For people who are interested in reef aquariums, you must have a reverse osmosis deionization system (RO/DI). This system will let you keep delicate corals and inverts without any harm.

The SpectraPure RO/DI system, unlike other models, produces 50% less wastewater. Indeed, the overall wastewater ratio for this device is 2:1, which makes it ideal for giving you purer water.

It is a budget-friendly unit that features a DI stage and many more great features to make the whole process easier for you. The system has two output speeds, 90 and 180 GPD. You can choose either one of them, depending on the tank size.

Furthermore, the device features laboratory grade resins, which is impressive because it will boost the production of pure water. Also, you get a 33% bigger MaxCap cartridge for the finishing stage.

It has five stages of filtration; sediment, carbon, membrane, and two DI. You can manually turn off the system through the in-line ball valve. Other features include a rust-free mounting bracket and precise fittings to set up the unit.

Furthermore, you’ll have a housing wrench, garden hose adapter, waste lines, and 6 feet feeding tube. It features many TDS meters, which will help you monitor the filtration process.

The flush valve will prolong the membrane’s life and prevent it from contamination.


  • Low rate of wastewater
  • Has many TDS meters
  • Features laboratory-grade resin


  • Unclear instruction manual

3. RO/DI Reverse Osmosis Aquarium/Reef System

Keeping an aquarium at home enhances its décor, but it does come with a lot of requirements. You are not only supposed to keep the tank clean and free of impurities but also make sure that the fish get proper food and pure water.

People often think filling the tank with tap water might be enough, but we know that fishes cannot survive the toxins and chemicals that are in the unfiltered water. For this reason, you must have an Reverse Osmosis system for your reef tank.

The RO DI Reverse Osmosis Reef System comes with six stages of filtration, unlike other models that only contain four stages. Even though it has more filters, the price is quite low for such a great unit.

It is very beneficial to have six filters because once you put the tap water in, it goes through such an extensive process of filtration that, in the end, you are rewarded with clean and fresh water.

There are two different capacities of GPDs; 100 gallons per day and 150 gallons per day. You can choose the one that works best for you and which is also compatible with the size of your water tank.

You will also have all the elements necessary for mounting it up, such as tubing, membrane, pressure gauge, and other essential hardware for installation.


  • Very budget-friendly
  • Six stages for filtration
  • Easy installation with multiple accessories


  • Doesn’t have TDS meter

4. LiquaGen RO/DI Aquarium Filter System

The reverse osmosis water mechanism is known for its effective method of filtering water. Moreover, new developments in technology have enhanced the filtration process to remove almost 99% of impurities from the water.

With the LiquaGen RO/DI Aquarium Filter System, you’ll have a great experience because this system turns the tap water filled with toxins into clean and freshwater through its extensive process.

It is applicable for both freshwater and saltwater tanks. The six stages of filtration will filter even the worst kinds of tap water. This unit can deliver 100 gallons of water per day.

This unit is lightweight, which is impressive because you can move it around the house and place it anywhere you want. Another great feature is its removable polypropylene sediment filtrate, which will protect the membrane.

All minerals, rust and clogging particles are trapped in the filter to keep the blockage away from the membrane. It has two energized carbon cartridges, and what they do is eliminate chloramine, radon, and harmful organic compounds.

Other than the filter, you’ll get drain saddle valve, filter wrench, garden hose adapter, tubing, blue leak protection locks, automated shut-off valve, and a manual flush kit. All of these will help you set up the system in an efficient manner.


  • Several accessories for easy installation
  • Six stages of filtration, including deionization
  • Contains two energized carbon cartridges


  • No pressure gauge

5. Koolermax AR-122 Aquarium Reef System

The key to having a healthy and vibrant aquarium is using chemical-free water. Your corals, fish, aquatic plants, and other marine life flourish only if the tank water is compatible with their requirements.

We know that tap water isn’t the ideal option for marine and freshwater aquariums. To make it chemical and toxin-free, you need a reverse osmosis water system like the Koolermax AR-122 Reef System.

This system is adept at getting rid of chlorine once and for all. It also has a pressure gauge, which will let you know when to change the filters out. There are six efficient stages for filtering water.

The unit has a high production rate of delivering 120 gallons of water per day. Even at its lowest speed, it will provide 80 gallons of water per day. The DI filter is another excellent feature known for removing ions from the water to stabilize the pH level.

This unit can purify the water of delicate reef aquariums, and there is hardly any water wastage during the cleaning process. The water first passes through the sediment filter and two carbon filters.

Next, it passes through the sturdy membrane filter and finally undergoes 2 DI cleansing. For mounting the system, you’ll receive tubing, membrane, filters, and the pressure gauge for a quick and easy installation.


  • Excellent water sufficiency
  • Able to remove chlorine permanently
  • Six stages of the filtering process


  • Takes little time to mount

What Factors Make an Ideal RO/DI System:

The primary duty of any reverse osmosis system is to provide water free of contaminants. However, not all of them may cater to your requirements.

There are certain factors that you should weigh while choosing the most appropriate Reverse Osmosis system. For instance, how big is your tank, how many stages of filtration, etc.

Here we have compiled a list of considerations you should be mindful of before buying the best Reverse Osmosis system for a reef tank.

·      The Size of Your Aquarium:

This is an essential consideration because it would determine the amount of water you need. If you have a large tank, then certainly, you need a system that can filter large quantities of water.

While purchasing or reading reviews of a product, keep an eye out for the GPD (gallons per day) score. For large tanks, the recommendation is to opt for a system with a rating of 50 or higher.

For smaller aquariums, you can choose one with a lower threshold. Not that a higher GPD rating would alter the price, it is a choice you have to make depending on your tank.

·      Filtration Stages and Geography:

The term geography carries a specific scientific connotation to it. Regardless, what we mean is here is, the strength of your filtration system depends on your local water condition.

In brief, if you live a locality that abounds in sediments, then the max or 5-stage filtration is necessary. Remember, this is an exceptional case only applicable to specific areas.

For users who don’t have this problem, the standard recommendation is an RO/DI system with four-stage filtration. It can perform with high capacity in most situations.

·      Comfortable Installation:

If you’re not an expert with the reverse osmosis system, chances are you’ll find it difficult to set up. Well, it’s not going to happen with all the products. Some of them (surprisingly) are quite easy to install.

Look for a system that’s easy to set up and maintain. Several manufacturers include all the necessary tools for proper installation. This addition would remove the headache of purchasing any extra tools.

A quick tip: maintaining the Reverse Osmosis system is also crucial. You can comfortably look after products that feature effortless installation. Remember, you must change the filler cartridges from time to time. A system that is easy to maintain will make your task convenient.

·      Essential Certifications:

While looking for the best RO/DI system for reef tanks, keep in mind these two certifications- FDA (Food and Drug Administration) and NSF (National Sanitation Foundation). They’re a must-have.

These certifications ensure hygiene, water purity, and maxim contaminant elimination.

Although it is not essential, we would recommend choosing a branded RO/DI system. Not to play favorites, but bigshot manufacturers are usually the safest bet. You might find the product pricey at first, but over time, the investment would pay for itself.

So, it is up to you if you want to purchase a shoddy product with half the price and get swindled. In contrast, paying a high price for quality would be cheap in the long run.

Components of your Reverse Osmosis Unit

Understanding the components of your RODI system will help you to take educated decision while selecting it for your aquarium. The components are –


Types of membrane is directly responsible for the amount of impurities it can handle. The semi-permeable membrane allows only water molecules to pass through by filtering out all unwanted constituents from the main water supply. Some high-output units feature multiple membranes ensuring higher efficiency.

The membrane is the most sensitive part of your RO unit and it may damage easily. So need to handle it carefully as it is the expensive part as well.


Pre-filters act as a defense mechanism to the membrane and sits before the membrane. They remove sediments, chlorine and other coarse components of your main source of water. By removing these components pre-filters protect potential blockages and the destroying of your expensive and delicate membrane.

Pre-filters should be replaced regularly to avoid any instances of failure. Otherwise, this will impact the efficiency and lifespan of your unit’s membrane.

Flow Restrictor

This valve helps to build up pressure in the system. Pressure is essential for the reverse osmosis procedure. Most reverse osmosis systems require a minimum pressure of around 2.8 bar (40psi). Ideal pressure protects the system from leaking or blowing apart.

Your reverse osmosis unit may also have a pressure gauge. This allows you to monitor the pressure of the main water entering the membrane. Insufficient pressure affects efficiency and can even stop the unit from working at all.

Flush Valve

This is an additional feature which can bypasses the flow restrictor. Flush valves rapidly rinses impurities from the membrane which prevents scaling or fouling of the membrane and keeps the membrane clean.

Flush valve could improve the efficiency, output and lifespan of a unit’s membrane. The membrane should be flushed daily if it undergoes heavy duty.

Frequently Asked Questions

Can I drink RO/DI water?

You may, but we would strongly suggest against it. Although it removes the impurities, the complete elimination of TDS (total dissolved solids) can have an adverse effect on your health. Researchers call it “hungry water” that can extract salt from your cells (not pretty)!

For drinking water you may need to install additional chamber to add minerals to the water.

Is there an alternative to the Reverse Osmosis systems?

Yes, there are other options. A common one is to purchase fresh saltwater from stores. However, we strongly recommend against it because it is a considerable waste of both time and money. In the long run, the RO/DI is the most efficient option.

Can I use deionized (DI) water for my tank?

No, the DI water is too pure; thus, not appropriate for a reef aquarium. In contrast, reverse osmosis (RO) water is abundant with salt and oxygen essential for the survival of aquatic life.

What kind of water filtration is suitable for my system?

To know this, you need to understand the sediment amount present in your tap water. You can contact your local water supplier to find out this information. For sediment abound areas, 5-stage filtration is recommended, whereas others can use the 4-stage system.

How often do I need to change the parts?

Knowing when to change the filter cartridge is essential. One convenient way to inspect the operation of your system is to use a TDS meter. Observe the reading, and if you see it going beyond 50 ppm, then know that the cartridge reached a critical threshold.

Maintaining the RODI system

Knowing when to change the different filters is essential for receiving consistent performance from your system. There are four aspects to keep in mind, and we gave a rough sketch on when to modify.

RO/DI Carbon Cartridges:

After a certain period of time the charcoal or carbon cartridge loses it’s effectiveness. And then it starts to release the toxicity back to the tank water. So replacing carbon should be practiced regularly. The ideal time to replace it is six months.

RODI Sediment Prefilter:

Similar to carbon cartridges, the optimum replace time is narrowed down to six months. However, if the TDS level of the tank exceeds 400, you should change this unit.

Reverse Osmosis Membrane:

They’re more durable compared to the other parts of the mechanism. The recommendation is the replace them once every 9-12 months. You can check the TDS level manually if you want to change it earlier or later than the standard time.

Final Thoughts

We hope this article was instructive and helped you select (or ease your doubts) the best RO DI system for reef tank.

If you’re still skeptic, read through our reviews, they’re comprehensive and contain all the necessary detail. You’ll find all the top-rated products that can fulfill your requirements.

Finally, with the essence of preserving all domestic marine life, we wish you a happy shopping!

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