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How to Choose the Best RO/DI System for Reef Tanks?
Setting up a successful freshwater or marine aquarium requires knowledge, skill, and ultimately lots of accessories. Among the accessories, to name a few we have to include a heater to warm up the water, a HOB filter or perhaps a canister filter to clean the water of any harmful debris, a lighting system to facilitate plant or coral growth, but an essential accessory for marine tanks is the best RO/DI system that will help you use the cleanest and safest water for your fish tank.
Reverse osmosis membranes are constructed from a membrane flat sheet that’s composed of three layers: a polyester fabric support base, a microporous poly cell phone layer, and a point two-micron thick polyamide barrier layer.
The good news is that nowadays it’s rather easy to find the best reverse osmosis system that will suit your needs, no matter you own or plan on setting up a reef tank or a freshwater aquarium.
The Reverse Osmosis systems have pad filters made from the finest activated carbon block filter vacuum – with a strong lattice structure they remove: limescale particles, chlorine, rust, dirt particles, germs, organic contaminants, Ckws, odor, color, pesticides, herbicides, bacteria.
The filters also remove nitrate from mains water. You no longer need water conditioners, saving money in the long run.
Finding the right RO/DI system for your aquarium has never been easier. Below, we are highlighting some of the best RO/DI systems currently available on the market.
Best Aquarium RO/DI Systems Compared
| Image | Product | Features | Price |
|---|---|---|---|
Best RO/DI System  | AquaFX Barracuda RO/DI Aquarium Filter | Filtration: 4-stage | Check On Amazon |
Best Seller RO System  | Aquatic Life RO Water Filter System | Filtration: 3-stage | Check On Amazon |
Durable RO/DI System  | LiquaGen RO/DI Aquarium Reef Water Filter System | Filtration: 5-stage | Check On Amazon |
Budget Pick RO/DI System  | Koolermax RO/DI Aquarium Water System | Filtration: 6-stage | Check On Amazon |
Easiest to Install RO/DI  | Express 6 Stage RO/DI Water Filter System | Filtration: 6-stage | Check On Amazon |
Great RO System  | 3-Stage Portable Aquarium RO Filter System | Filtration: 3-stage | Check On Amazon |
Full Pack RO/DI System  | LiquaGen Aquarium Reef RO/DI Water Filter System | Filtration: 6-stage | Check On Amazon |
High-end RO/DI System  | SpectraPure MaxCap RO/DI System | Filtration: 6-stage | Check On Amazon |
7-Stage RO/DI System  | LiquaGen Heavy Duty RO/DI Filter System | Filtration: 7-stage | Check On Amazon |
Top Quality RO/DI System  | Fountainhead RO/DI Water Filter System | Filtration: 6-stage | Check On Amazon |
Booster Pump RO  | iSpring RO Filtration System | Filtration: 5-stage | Check On Amazon |
Benefits of Using a Reverse Osmosis System
After setting up our list of the best RO/DI water filtration systems available on the market, let’s explain why almost every reefer uses reverse osmosis deionized water and what each stage in RO/DI systems does.
We’re going to dive into a piece of equipment that you can find along with every long-term successful reef tank out there – the reverse osmosis deionization system. Well, RO/DI filtration systems look rather complicated with all the canisters, filters and tubes. But no need to worry – it’s probably one of the easiest things you’ll ever install or use.
If you feel like getting more advanced, you can hook the system up permanently under your sink, mount it on your wall, or even set it up with a pressurized tank for purified drinking water.
When you first decide to start a reef tank, there are a few comprehensive options. But most people select tap water with some conditioner or the best choice: reverse osmosis-deionized water. Well, as always, there can be exceptions to the rule, but every long term successful reef tank I’ve seen uses a RO or RO/DI filtration system. As a new reefer, most of us are just concerned about chlorine, which can be simple to treat with some water conditioner.
There are two main concerns with our city water that go beyond simple chlorine.
First, it can contain nutrients like phosphate and nitrates, which feed algae growth, slowdown calcification, and uncontrolled coral growth. Fish food will almost always be the most significant source of these nutrients, but maintaining high-quality, low nutrient water should include various efforts.
The second concern is about general contaminants, like metals and chemicals found in many water sources: farm runoff, old sewer systems, your home’s copper piping, less than ideal water treatment plants and a hundred other things can all add unwanted contaminants to your home’s tap water.
However, the more you learn about tap water, the less you may want to drink it as well. What your city or the EPA considers safe levels of disinfection byproducts, copper, lead, arsenic, mercury and a laundry list of inorganic or organic compounds might not be the same thing you want to consume, provide to your kids or pour into a closed system like a reef tank.
To effectively deal with all these contaminants from our tap water, I believe it’s just easier to buy an inexpensive RO/DI water filtration system and remove as many of these things as possible yourself.
Key Benefits and How RO/DI Units Work
A reverse osmosis filtration process will remove a vast majority of water contaminants by as much as 98%. The deionization, which is the second step, can approach a hundred per cent removal with many common water contaminants making RO/DI units ideal for a reef tank.As an alternative, you can purchase reverse osmosis water at most groceries, or fish stores. This is often convenient and reasonably affordable. But you’re at the mercy of how well the store takes care of their machine.
However, always aim for well-known fish stores since they are often much better options because they know the importance of maintaining their RO/DI systems for clean water which can be safely used in a reef tank.
Anyway, I consider that’s always a better thing to have at home one of the best aquarium RO/DI system at home, so you can efficiently deal with water changes at any time.
RO/DI Systems Filtration Stages
The best RO/DI water filtration systems for aquariums are equipped in most cases with five or more filtration stages.
Sediment Filter in RO/DI Filtration Units
Such RO/DI units for reef tanks have a single sediment filter, two carbon blocks and RO membrane, and the final stage is a DI resin cartridge. The sediment filter is pretty much as it sounds, a filter designed to capture sediment and dirt, so the more expensive carbon blocks don’t get clogged with water debris from the initial filtration stages.
Though these filters all look the same, they come in various qualities. Using higher quality sediment filters will better protect your other filters, and as such, the replacement frequency of cartridges will be reduced. They will also help maintain higher water pressures feeding the system, significantly increasing the filtration’s overall performance.
Carbon Blocks in RO/DI Filtration Units
The next in the composition of an RO/DI filter system are the carbon blocks. They’re typically installed in series with the first one having a larger micron size often between 5 and 10 and the second one is usually less than one micron. These carbon filters primarily remove chlorine and volatile organic compounds like pesticides, herbicides and hundreds of other human-made chemicals. And that’s not all!
Carbon filters also remove unwanted tastes and odors. When looking for carbon cartridges for your RO/DI unit, I suggest picking a brand made in the USA with US water quality standards instead of cheap imported versions and definitely look for the NSF certified seal, which means these filters have been tested to ensure their quality.
While some reef RO/DI filtration systems have one carbon block, a second carbon block brings some advantages. The most significant advantage is that it provides more extended water contact for complete unwanted elements removal.
A second advantage is that the smaller micron carbon blocks are typically better at challenging to remove volatile organic compounds, and running two blocks gives you a longer replacement window. So it’s less critical to change them precisely on time.
RO Membrane in RO/DI Filtration Units
The next filtration stage happens in the RO membrane in the white canister up top. This is the filter that does a vast majority of the work. The rest of the filters were more or less, just prepping the water for the membrane. A well functioning RO membrane will typically remove between 96 and 98 per cent of the total dissolved solids or TDS found in the water.It’s just a thin membrane rolled up, allowing water molecules to pass through, but rejects most contaminants and sends them out with the wastewater. If you maintain the pre-filters properly, this membrane can last as long as three years or even longer. After the water leaves the RO membrane, it’s relatively pure, and this is the type of water most people would drink.
Let’s take the water one step further with a final polish through deionization at the last stage.
DI Resin in RO/DI Filtration Units
The resin comes in place as nutrients like phosphates and nitrates are some of the more problematic elements for an RO membrane to remove. So while the RO system has substantially purified the water, there may be disproportionately high levels of these nutrients that the DI resin will help reduce.
In the aquarium industry is fairly common to use a DI resin containing a pH-sensitive dye that changes color to tell you when the resin is depleted. One of the more common resins changes from a dark blue to a golden brown as it depletes. We don’t use DI resin alone because it only removes contaminants with an electrical charge and in most cases, that would be cost-prohibitive.
It’s much more cost-effective to remove a vast majority of the contaminants with an RO system then use DI resin for the final polish.
Furthermore let’s pick and review each unit from our best RO/DI systems for aquariums listed in the table.
1. AquaFX Barracuda – Best Overall RO/DI Water Filter System
For the asked price, the best RO/DI product one can get is definitely the AquaFX Barracuda RO/DI system.
It filtrates the water in 4 stages and it comes with a 2-micron chlorine guzzler carbon block filter for extra purification.
The system features a high flow and high rejection TFC membrane and a pressure gauge is included to allow users of unsafe ranges to successfully use the system.
Convenient price and very sturdy unit:
The AquaFX Barracuda RO/DI system has been on the market for many years and it has earned its reputation. Customers all over the world are very happy with the unit and the price they paid for it.
It is extremely easy to set up and change its filters. You can easily place it under the sink, or in the basement right next to the outtake water pipes. It works like a charm with an 85 PSI water pressure. If your water pressure is lower than this, perhaps a booster could be ideal. Get 0 TDS water in no time with the AquaFX Barracuda RO/DI system.
For example, if you’re only interested in measuring the water TDS levels, you may take a look at our article on the best TDS meters for aquarium.
It has been reported the water outtake might be larger if you use higher temperature water, but bear in mind that the warmer the water, the shorter the filters’ life.
- A reputation earned over the years of a great RO/DI system
- Easy to install anywhere
- Very sturdy, customers have been using it for years all over the world
- 4 stage filtration to ensure 0 TDS water
- Can perform poorly if the water PSI is low
2. Aquatic Life RO Buddie – Largely Sold RO System
The Aquatic Life RO Buddie water filter system comes in three options:
– 50 GPD four-stage filtration
– 50 GPD three-stage filtration
– 100 GPD three-stage filtration
Depending on your needs and the actual tank you plan to set-up, or have already set-up, a particular option would be the best.
However, with the 50 GPD four stage filtration including the DI kit, you’ll get 0 TDS, making it an ideal option as a RO kit overall.
Different options available:
RO Buddie 3 Stage 50 & 100 GPD RO Systems
These lightweight, sturdy, and compact RO units (no DI) offer economical filtered water! The systems come with unbelievable affordability and functionality showing the very compact design and providing a reliable source of RO filtered water that you can use for your aquarium. The package includes the RO unit itself, cartridges, membrane, faucet adapter, and membrane wrench.
RO Buddie 50 GPD 4 Stage RO/DI System
This RO/DI 4 stage filtration system offers a great 0 TDS measured at its out valve. The package includes the improved DI color changing mixed bed resin cartridge with MBD-30-NG nuclear grade resin. The cartridge media removes most of the remaining total dissolved solids (TDS) from membrane-filtered water, and the outcome is purified water with an average conductivity value of ~0.1µS/cm.
Quick and very easy to install:
The RO Buddie RO/DI systems use thin-film composite (TFC) membranes combined with carbon and sediment pre-cartridges to effectively and efficiently remove harmful elements such as heavy metal ions, dissolved solids (TDS), chlorine, and particulate matter from the regular tap water. The 4 stage RO/DI system includes a DI resin cartridge to remove most remaining TDS.
- Affordable and very efficient
- Easy to handle and install
- You can achieve 0 TDS with the 4 stages RO/DI system that includes a DI resin cartridge
- The unit works best indoors at room temperature
- The water pressure should be at least 60 PSI for optimal GPD ratio
3. LiquaGen 5 Stage RO/DI System – Durable & Sturdy RO/DI Water Filters
If ultra-pure water is what you’re looking for, then you probably should go no further than here.
It is the ideal RO/DI system for any type of aquarium, whether you have a reef tank or a freshwater one with Discus for instance.
It is very easy to install and maintain, so if you’re into RO/DI business for the first time, the LiquaGen 5 stage RO/DI system could be the best RO/DI system for your needs.
5 stage RO/DI system
While most RO/DI systems available on the market come in 3-4 filtration stages, the LiquaGen brings an outstanding 5 stage RO/DI system.
In the first filtration stage, the Polypropylene sediment removes any dirt, rust, dust chemical resistance, sand and scale particles.
In the second filtration stage, the UDF activated carbon removes chlorine, organic chemicals, tastes, odors, and other impurities from tap water.
In the third filtration stage, the Coconut carbon removes any free chlorine leftovers, taste, odor, and organic chemicals that make the water impure. The filter provides enhanced absorption and efficiency.
During the fourth filtration stage, the RO membrane removes up to 99% of total dissolved solids (TDS) and contaminants such as arsenic, lead, fluoride, chromium, radium, bacteria and much more.
Finally, during the fifth filtration stage, the Deionization cartridge kicks in, dealing and removing all mineral ions such as cations from calcium, sodium, copper, and iron, but also the anions such as chloride and sulfate.
- 5 stage filtration offering perfect 0 TDS water
- Easy to install in just minutes
- Perfect for first time RO/DI systems users
- Extremely happy customers so far
- Due to high demand, sometimes shipping can take a little bit longer
4. Koolermax AR-122 – Best Budget RO/DI Water Filtration System
The system comes with the RO unit, pressure gauge, all filters, and additional installation hardware that’s required.
The Koolermax AR-1222 system filtrates the tap water in 6 different stages, and reaching a 0 TDS water is not a big deal, although if the tap water’s TDS is higher than 300, could be that the RO/DI system might face difficulties.
6 stage RO/DI filtration system
In the first filtration stage, the 5 micron sediment filter removes rust, sand, dirt, sediment from the water.
In the second filtration stage, the coconut shell activated carbon block filter removes chlorine, chloramines and odor.
In the third filtration stage, the 2nd stage is actually repeated to ensure a 100% removal rate of chlorine.
In the fourth stage, the 120GPD reverse osmosis membrane removes up to 98% of contaminants and dissolved minerals.
And finally, in the fifth and sixth stages, the DI filter comes in action to further purify and reduce the minerals so the water can be used for aquarium or other applications.
- 6 stage filtration system to get 0 TDS water
- Good price and can be fitted to a large variety of appliances
- Easy to maintain
- No TDS controls in and outline
- Filters can only be purchased from Koolermax
5. Express 6 stage RO/DI System – Easiest to Install RO/DI System
The Express Water RO/DI system brings a 6 stage filtration unit that your fish and your house appliances will simply love.
A quick win about the Express RO/DI system is the fact that plenty of its components come already assembled, so a lot fewer headaches for you during the installation process.
Part of the filtration process is also the water softener which is great for softening hard water at your point of use without adding any sodium.
The best equipped RO/DI system:
Compared to other RO/DI systems, the Express RO/DI system filtration in 6 stages, comes equipped with unique features.
Double sealed filters to preserve the filters and make their life a lot longer. This also prevents any unwanted leakage. Each filter is double sealed to provide the best filtration efficiency and value.
The leak stop valve shuts off water flow if any excess water is detected. A fabric disk placed on the floor next to the RO/DI system and will shut the system if it absorbs any water from potential leakages.
In the package, the brass feed adapter and quick-connect adapter are included, meaning you won’t have to go to the hardware store to buy parts. The feed adapter fits the two most common sizes of under sink pipes 1/2″ and 3/8″.
- Easiest to install RO/DI system
- Comes with plenty of components already matched
- A high-tech system with plenty of features
- Labeled color matched system so you know what goes where at a glance
- Customers complained about the water could be smelly
- Some components might need to be re-attached again, although they come assembled already
6. Portable Aquarium RO System – Best RO System for Freshwater Tanks
If you’re looking for a RO filtration system for your freshwater tank, this can be an ideal candidate.
The filtration is processed in 3 stages and it reduces 99% of the heavy metals like Arsenic, Lead, Mercury, Fluoride, Hardness, Cadmium, Chlorine, Taste, Odor, and more 1000+ contaminants.
The installation and filter replacement is pretty easy. And there’s even more good news: this RO system does not have a tank, doesn’t need electricity nor any plumbing.
Compact and highly efficient:
This is the best RO system that you can think of. It is portable, has small dimensions, and is it’s really lightweight. This makes it just perfect for an apartment, RVs, business travel, vacation, yacht, boat, mobile home, or anywhere you need to have pure water.
It operates best at 70 PSI water pressure, with a temperature of 77 F or 25 C. NaCl concentration: 250 ppm. recovery: 15%. Filter fineness down to 0.0001 microns, but different water parameters might have different results.
- Very convenient dimensions and weight
- Extremely easy to set-up
- No tank, electricity, plumbing required
- No DI filtration possible with this unit
7. LiquaGen Reef RO/DI System – Includes TDS Meter & Pressure Gauge
Undoubtedly one of the best manufacturers of RO/DI systems currently available on the market, Liquagen never disappoints.
Whether you have a marine aquarium of a freshwater one, this is a sturdy RO/DI system with outstanding performance.
Similar to the other LiquaGen RO/DI systems from this blog post, the filtration is done in 6 stages, ensuring and outcome of 0 TDS water.
6 stage RO/DI system
While most RO/DI systems available on the market come in 3-4 filtration stages, the LiquaGen brings an outstanding 6-stage RO/DI system.
In the first filtration stage, the Polypropylene sediment removes any dirt, rust, dust chemical resistance, sand and scale particles.
In the second filtration stage, the UDF activated carbon removes chlorine, organic chemicals, tastes, odors, and other impurities from tap water.
In the third filtration stage, the Coconut carbon removes any free chlorine leftovers, taste, odor, and organic chemicals that make the water impure. The filter provides enhanced absorption and efficiency.
During the fourth filtration stage, the RO membrane removes up to 99% of total dissolved solids (TDS) and contaminants such as arsenic, lead, fluoride, chromium, radium, bacteria, and much more.
Finally, during the fifth and sixth filtration stages, the Deionization cartridge kicks in, dealing and removing all mineral ions such as cations from calcium, sodium, copper, and iron, but also the anions such as chloride and sulfate.
- 6 stage filtration offering perfect 0 TDS water
- Easy to install in just minutes
- Perfect for first time RO/DI systems users
- Extremely happy customers so far
- Comes with 2 DI resin filters
- The installation instructions could be improved
8. SpectraPure MaxCap – High-end RO/DI System for Reef Tanks
Comes equipped with intake and outtake TDS meters, which are very helpful especially if you are planning to use the best RO/DI system for your reef tank or perhaps for your freshwater aquarium.
It is an economical RO/DI system with its 2:1 waste ratio that generates 50% less wastewater.
Durable and well equipped RO/DI system:
Its RO membrane life is naturally prolonged with the help of the manual flush valve. It comes equipped with an automatic in line shutoff valve that helps save a lot of water, compared to other reef tanks RO/DI systems.
Durable, with a no rust mounting bracket, a 6 foot feed tubing, 8 foot product and waste lines are included in the package. Housing wrench for easy filter removal is also supplied, along with a garden hose adapter for easier tap water hookup. Product dimensions are as follows: 20″ x 7″ x 16.
With the SpectraPure MaxCap RO/DI system, you will get ultra-high purity DI water at a very economical price, as the total water production cost is simply cut in half!
- 3 years warranty from the manufacturer
- Relatively easy to setup
- Very happy customers so far
- Comes fully equipped with lots of necessary parts that some systems don’t offer
- RO/DI system can produce 20 gallons of 0 TDS water in about 3 hours
- Needs to be mounted
9. LiquaGen Heavy Duty – Best 7 Stage RO/DI Water Filtration System
Perhaps the ultimate and the king of all RO/DI systems out there available on the market. As the name speaks for itself, the heavy-duty RO/DI system from LiquaGen produces up to 150 GPD in a 7 stage filtration system.
It is ideal for reef tanks, saltwater, and freshwater aquariums by the process of DI, ensuring zero ppm water, optimal for fish, coral, and other marine life & plants.
7 stage RO/DI system
While most RO/DI systems available on the market come in 3-4 filtration stages, the LiquaGen brings an outstanding 7 stage RO/DI system.
In the first filtration stage, the Polypropylene sediment removes any dirt, rust, dust chemical resistance, sand and scale particles.
In the second filtration stage, the UDF activated carbon removes chlorine, organic chemicals, tastes, odors, and other impurities from tap water.
In the third filtration stage, the Coconut carbon removes any free chlorine leftovers, taste, odor, and organic chemicals that make the water impure. The filter provides enhanced absorption and efficiency.
During the fourth filtration stage, the RO membrane removes up to 99% of total dissolved solids (TDS) and contaminants such as arsenic, lead, fluoride, chromium, radium, bacteria, and much more.
Finally, during the fifth, sixth, and seventh filtration stages, the Deionization cartridge kicks in, dealing and removing all mineral ions such as cations from calcium, sodium, copper, and iron, but also the anions such as chloride and sulfate.
- 7 stage filtration offering perfect 0 TDS water
- Easy to install in just minutes
- Perfect for aquarists that need plenty of RO/DI water
- Extremely happy customers so far
- Comes with 2 DI resin filters
- There have been units reported to have leaks and were replaced
10. Fountainhead RO/DI System – Top Quality & Performance RO/DI Reef System
A relatively newer RO/DI water filtration system for reef tanks and freshwater tanks, the Fountainhead RO/DI system comes with a 6 stage filtration.
The RO system, combined with a DI after the filter, will give you the lowest TDS reading for your aquarium water supply.
DI Resin is necessary to reduce Total Dissolved Solids (TDS) to zero and is the last stage of the RO/DI unit. It is not necessary to use the expensive DI cartridges that other RO manufacturers provide.
You can just buy a refillable DI cartridge for the Fountainhead RO/DI system and fill with DI resin. You’ll save money like this and the results will be just identical.
- Clear cartridges are refillable
- Newer generation product with more modern components
- Very happy customers so far with no complaints
- Finest RO/DI system quality
- 6 stage filtration with dual DI – 150 GPD
- Couldn’t say any
11. iSpring RCC7P RO Filter – Ultimate RO Water Softener for Aquarium
Although it’s last in our list on this blog post, that’s nothing but a number. The iSpring RO system is simply a great choice as a RO system for your freshwater aquarium.
It comes pre-equipped with a near-silent booster pump that aims to reach proper PSI for the system.
Filters out 1,000+ water pollutants including common adversaries chlorine and fluoride while the thin-film composite semipermeable RO membrane filters down to 0.0001 microns.
- Comes with a booster pump that deals with low water PSI
- Finest micron, layered protection
- 1-year money-back guarantee
- Lifetime support
- 5 stage filtration
- No DI available with this unit
To conclude
Although we listed quite a few RO/DI water filtration systems above, and things could still be a little bit confusing, we hope we were of help as we did our best to narrow down from all the available units to this top list.
Carefully research each and every unit before deciding which one is really the best RO/DI system for your needs, depending on the aquarium you have.
As per our recommendation, we find the AquaFX Barracuda, the best RO/DI system overall.
It combines the best technologies and components, providing top notch filtration in 6 stages.
Can reverse osmosis water be used in a fish tank?
Reverse osmosis water is definitely a great starting point for any aquarium owner seeking to create ideal water conditions for their fish and coral. RO water is completely free from toxic chemicals that are harmful to fish, such as chlorine and chloramines, is neutral in pH, and contains no water hardness.
Can reverse osmosis water be used in African Cichlids tank?
The answer isn’t simple. On the one hand yes you can. But then the pH needs to be matched to the one your fish are used to.
On the other hand and more importantly, Cichlid Lake Salt should be added, to reach the desired water hardness.
Is reverse osmosis water needed for Discus tanks?
RO water is not necessarily required to keep Discus, but to successfully breed them, yes – RO water is required. Otherwise, the hatching ratio will be disappointing.
