A reverse osmosis water system works to filter the water, removing any contaminants so that you end up with clean water.
The RO/DI systems have a great reputation as being an effective way to filter the water; new advances in technology have improved the filtration capability to the point of removing up to 99 percent of the impurities.
You can now get RO/DI systems for reef tanks, saltwater aquariums. You simply have to make sure that it’s the best choice for your aquarium model before buying it.
Table of Contents
What is the Best RO/DI System for an Aquarium?
Reverse osmosis systems come in different sizes, shapes, and functionality. You should not have to buy all of them, but just the one that works great for you.
It is important that you now learn what makes the best RO/DI system for aquariums.
The Filtration Process and Stages
Depending on the type of RO/DI water system, it can have 4 to 6 filtration stages. It is during these stages that the water is purified to remove any contaminants and make sure it is clean for your aquarium fish.
These systems often have additional filters that remove the odor and improve the taste, but one that ensures all the dirt is removed should be sufficient for use in an aquarium.
Brand and Certifications
Choosing the right brand is crucial to ensure that you always end up with a high-quality model that works great in different aquariums. You can have a single filter system for both freshwater and saltwater aquariums.
The top brands have reputations they want to maintain. This is the reason you are likely to find one brand having a better reputation than the others, and it is always better to select the best product from the top brands.
Beyond just buying from the best brand, you have to make sure that the filter also has the right certifications. The most common certifications would be FDA and NSF certificates. If your filter has these two approvals, you can relax, knowing that you have the right product.
Installation and Maintenance
After you select and purchase one, you would have to install the reverse osmosis water system. Depending on the design, various filter systems can be either hard or easy to install. You can check out several RO/DI systems to see which ones would be easiest to install.
Some manufacturers include all the mounting hardware you will need, while others include nothing in the box but the product and instructions.
It is not about the installation alone, but also the maintenance of the system. Ideally, you want it to be easy to install new parts if anything breaks. If a model is designed so it’s easy to swap out parts, it’s easier to perform necessary maintenance on that water filter system.
Usability
You have to consider how easy or hard it would be to use the reverse osmosis system that you choose. There is no need to buy a model that will take a lot of time to just configure or operating it.
The idea is to end up with the best reverse osmosis system that comes with easy-to-use controls. It is from these controls that you can operate the system and create clean water for your aquarium.
Reviews
Reviews are the best place to learn about the best RO/DI systems for your aquarium, reef tanks. In their reviews, users explain what they liked or did not like about the system. It’s important to take the time to learn about the RO/DI system from reliable reviews.
Not all reviews are genuine, as some manufacturers pay reviewers to write positive reviews. It is best to seek out a reliable review site to read reviews on.
The Best RO DI Systems For Saltwater Aquarium, Reef Tanks
RO/DI System for Aquarium Reviews
1. AquaFX Barracuda RO/DI Aquarium Filter

This model is the best thing you can get for your money. Many people have used it for both freshwater and saltwater aquariums. You might be thinking that it will cost you a lot, but you would be surprised as it is quite affordable.
It is not just about the attractive price, but also the strong purification process that makes this model appealing to so many people. With quality filters in place, you can be sure it will always deliver the best water in the end, with no impurities.
Pros
- It has a faster outflow as compared to other models
- It has a great purification process
- Easy to set up
Cons
- Seems to have a high water wastage ratio
2. Koolermax AR-122 6-stage RO+DI Aquarium Reef RO system

Some of the top-selling points of this model would be the six-stage filtration process and the high capacity of 120 gallons. Not many RO/DI systems for reef tanks have such a capacity. Even aside from this, there are additional features that make it the best for you to use in your aquarium.
The previous model had issues with water wastage ratio. You will be happy to know that this one doesn’t have that problem.
The six-stage filtration system helps a lot when it comes to removing all the possible contaminants from the aquarium water. The additional DI filter is great for removing the ions from the water.
Pros
- Comes with a faster outflow
- It has a lower water wastage ratio
- Addition DI filter to remove ions
- It is highly effective when filtering the water
Cons
- A bit of fiddling is needed to fix it
3. Aquatic Life RO Buddie Three Stage Reverse Osmosis

The manufacturer offers this model in two capacities: 50 gallons per day or 100 gallons per day. You simply have to choose the one that best suits your needs.
The three-stage filtration process comes with an RO cartridge, carbon and sediment filters. They work together to ensure that you do not have to worry about metal ions or any other types of contaminants.
The manufacturer is already known to produce the best products in the aquarium field, so it’s no surprise that this model is so great. With the addition of new technology for water filtration, you should end up with the very best reverse osmosis filtration system available.
Pros
- It is easy to install, even for a person new to the process
- It allows for additional filtration stages to be added
- Easy to perform maintenance on it
- It has a compact size for easy installation
Cons
- You are likely to experience leaking if it is not fitted properly
4. SpectraPure MaxCap RO/DI System

The capacity of 90 gallons per day should be just perfect for most aquariums. You can now be sure that your aquarium will end up with the best, cleanest water each time you use the RO/DI system.
It comes with a 99 percent rejection film that is important to make sure that the contaminants are all removed. With this film, you can always be sure you have the clean water you need.
This model is made of strong materials, which is important for keeping the device in pristine condition. The non-rust mounting bracket will make sure that the filter remains in usable condition. The use of a manual flush valve will also help the membrane to last longer.
Pros
- It comes with a lower water ratio
- The mounting brackets do not rust
- Comes with the automatic inline shutoff valve to save water
- It has a 99 percent rejection thin-film
Cons
- It is quite pricey
5. LiquaGen 5-Stage Reverse Osmosis/Deionization

This product is designed to be great for multiple applications. The manufacturer claims it can be used in aquariums, labs, or any other place where you need ultra-pure water.
To make it easy for the user to install, the manufacturer has pre-assembled it. You will simply have to attach it to your aquarium and turn it on.
The 5-stage filtration process should provide enough room to filter out the different contaminants from the aquarium water. The quality of the water you get from this RO/DI system can also be used for cooking or even drinking. The high rejection membrane provides the ability to handle many contaminants common in aquariums.
Pros
- It has a high capacity
- It has multiple applications
- The membrane has a high rejection rate
Cons
- The GPD often start at low rates but might improve with time
6. Express Water Deionization Reverse Osmosis Water Filtration System

Everyone knows that deionized water tastes better and can produce meals that are more delicious. Plus, deionization is excellent for your water-using appliances.
If you have a fish tank (saltwater or freshwater), your fish are going to like you. The Express Water brand can help your marine life live longer and healthier lives.
When you use this product, you can remove a lot of bad things from the water. These include fluoride, chlorine, and lead. You can also get rid of bacteria, arsenic, calcium, and nitrates.
This product, along with the filters, can have you drinking healthier water. Plus, you do not need to hire someone to install it. The instructions are quite easy to understand.
There is also an automatic mechanism. This means your water tank fills up with water on demand. That way, you don’t have to activate the system.
It also comes with coconut carbon filters. These give you better quality and a clear, natural water taste.
You’ve also got an emergency leak detector. This shuts off the water flow automatically to protect your home.
Pros
- Fast flow rates
- Always ready when needed
- Quick and easy filter changes
Cons
- Can have leak issues
- Might have higher PPMs
- Smelly water
7. LiquaGen Aquarium Reef Reverse Osmosis RO/DI Water Filter System

Those who want the best filtration system are going to like the LiquaGen brand. It’s ideal for saltwater, freshwater, and reef tanks. Plus, you can use it for other applications.
There is no membrane flushing needed. Also, it installs in just minutes. Therefore, you do not need to hire a professional to do it for you.
This patented permeate pump can reduce your wastewater by up to 80 percent. It can also increase the water flow up to two more times. If that weren’t enough, you don’t have to use electricity for it to work.
People who have low water pressure can still use this system. It automatically ensures that the flow rate stays at the right level.
You are going to like the pressure gauge. It is easy to read. Immediately tell when your filters need to be changed and see your water pressure levels.
Of course, this means that you get the best water filter performance all the time. Those who care are going to appreciate that this product is made in the USA.
Pros
- BPA-free
- Long-lasting filters
- Leak-free fittings
Cons
- Hard-to-read instructions
8. Fountainhead Water System RO DI Aquarium/Reef System

If you’re looking for a dual system for aquariums and drinking water, the Fountainhead brand is suitable. It’s a pre-assembled system, which has two different outlets.
The first outlet works well for household needs, such as cooking and drinking. You also get a second outlet. This one works well when ultra-pure water is required, such as laboratory testing and aquarium use.
There are six filtration stages. The first one removes micron sediment while the second one removes granular-activated carbons. With the third stage, you can remove micron carbon blocks, and the fourth stage can remove RO membranes.
For the fifth stage, you get a mixed bed with a color-changing filter in a clear housing. The sixth stage is your inline post carbon filter.
You are always going to get a constant supply of pure water with this product. Of course, there is a manual valve so that you can flush the membranes periodically. This prevents the TDS creep issue many people have.
Pros
- Easy to install
- Filters water quickly and efficiently
- High-quality
Cons
- Instructions for installation hard to read
- Some leakage
9. LiquaGen Heavy Duty & High Capacity Aquarium Reef Systems RO/DI

The LiquaGen Heavy-Duty filter system works well for a variety of things. They include lab testing, aquariums, and drinking water.
This is a pre-assembled system, so it doesn’t require a lot of work to install. In fact, most people can fit it in just five minutes.
It contains a manual flush valve. Therefore, it’s a superior system design than other RO/DI options on the market. This can increase the life of your unit, reduce leaks, and save time.
While it is important to flush the system every few months, it isn’t hard to do. The instructions explain it all, so you aren’t going to be confused.
This product uses a high-rejection RO membrane. That means it can remove nitrosamines and other precursors. Plus, the product is made in the USA.
You’re going to find a use for this filter system. It works well in reef tanks, as well as saltwater and freshwater aquariums. With the deionization process, you can ensure no PPM in the water.
Pros
- Leak-free Fittings
- BPA-free
- High Octane Performance
Cons
- Must tighten fittings periodically
- Challenging to change filters
10. Geekpure Portable Aquarium Reverse Osmosis Water Filter System

Are you looking for an efficient RO water filter system? If so, the one from Geekpure might be ideal. It features three stages of filtration.
Therefore, you can get things down to a 0.0001 micron. Plus, it reduces up to 99 percent of arsenic, mercury, lead, and heavy metals. It can also remove fluoride, chlorine, and cadmium.
You’re going to have better-tasting water that doesn’t have any odor. Though it can be used for drinking water, it is designed for aquariums.
You get high-quality components. All of the fittings, tubes, and membranes comply with NSF/ANSI standards. Therefore, you get safe and healthy drinking water.
It’s possible to install this product anywhere. Plus, the ratio of waste to pure water is 2:1. While this filtration system doesn’t come with a faucet, you can purchase a drinking water kit separately.
That means you can use it in apartments, mobile homes, and RVs. It’s suitable for vacations, yachts, and business travel.
Pros
- Great value
- No leaks
- Easy to assemble and install
Cons
- Installation instructions hard to understand
- Must check all connections to prevent leaks
- Challenging to find replacement filters
Conclusion
From the many options you have seen above, it is likely that you have learned several things about how to choose the best reverse osmosis system. These systems can deliver the quality performance that you really need when you make the right choice and buy the right model.
Comparing different models is always the best way to end up with a system that delivers the best performance. With the right RO/DI system, you will be ready to handle any impure aquarium water.
I have been raising fresh water tropical fish for over 40 years. I am reviewing RO systems with the intention of taking very hard well water and making so I can buffer it with chemicals or peat and create a PH of around 6.5. I want to raise angelfish. My current water coming out of the tap has a PH of 8.2 and a TDS of over 400. The GH and KH are so high that that they do not even register on the chart. This water is great for African Rift Lake Chiclids and any community fish that like hard water but not good for fish that prefer acidic water like angles, rams, discus, etc. I need input on how to engineer this water conditioning. I already have a Culligan water softener. What say you?
Rob Schick,
Honestly we have well water and are in the same situation. I haven’t had fish for 40 years but I have studied them and read up on the tanks I have had for the last 20 years. The best solution that will get that water where you want it will be the reverse osmosis, Also just make sure the Nitrates and Nitrites are 0, use a heavy metal remover along with charcoal filtration with your BIO Wheel and R/O system, put live plants in the tank as well which in combination should get that water within a few weeks primo for your first introductory fish. keep the temp right and algae under control and your set. As you probably know the most natural you can keep it the more apt you will be successful. Nature has a lot of filtration through the ground and sun. Another thought would be to add Ultraviolet light inline.
One other thing add SALT that’s a big one for proper natural environment for several reasons.
I have a 50 gallon tank plus a 10 gallon isolation tank. I moved to an area where tap water has a ph of 8.6 and is very hard. I’m considering getting an RO system. But know nothing about them. Do they attach to the tank, go under the tank with pipes for intake and return, or do you put I on a fauset under a sink and use it to fill/refill the tank?
Aquatic Life RO Buddie Three Stage Reverse Osmosis has 3 stage RO system and a 4 stage RO/DI system. What is the difference and will it matter if I’m doing a fish only saltwater tank?