What Will Remove Nitrates From Aquarium Water?

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A positive nitrate test is pretty common in home aquariums, and it immediately raises one question: what can actually remove it? As I asked this question so many times in the past, I decided to gather everything that I know into one article.

These are the main ways to remove nitrates from aquarium water:

  • Water changes
  • Water conditioners
  • Reverse osmosis
  • Ion exchange

As we move forward, I will elaborate on each option, and discuss how you can implement it in your aquarium. I will also discuss what I believe is the best way to get rid of nitrates, and why routine water changes may sometimes fail to do so.

Changing the aquarium water is one of the best ways to remove toxins like nitrate.

What Will Remove Nitrates From Aquarium Water?

How do you remove nitrates from aquariums? A paper in IOP Publishing LTD (IOP Conference Series) explored the efficacy of the Indian almond leaf.[1]

They added Indian almond leaves to the water in powdered form and, in doing so, recorded a reduction in ammonia levels.

In that regard, you could argue that Indian almond leaves are an effective solution to nitrates. 

After all, you get nitrates when bacteria convert ammonia into nitrates. If you remove ammonia, nitrates won’t form.

This sounds like a rational solution but it can’t help you if your tank already has nitrates. Boiling the water is just as ineffective.

If anything, boiling tends to concentrate contaminants instead of removing them.[2] Fortunately, you have plenty of practical solutions at your disposal, including:

1. Reverse Osmosis

A paper from Hawaii’s water resources research center explored a reverse osmosis system that relied on wind power to remove nitrogenous waste from aquariums.[3] 

However, conventional aquarists do not require wind-powdered reverse osmosis systems to combat nitrogenous waste. Any reverse osmosis system they can afford will do.

The objective of reverse osmosis is to force water through a membrane with microscopic pores. 

The semi-permeable membrane acts as a sieve. The pores are small enough to separate contaminants like nitrates from water.

Rather than specifically applying this method to your tank, you are better off installing a reverse osmosis system that serves the entire house. The system will keep the water it sieves in a storage tank.

You can funnel that water through your taps. This guarantees nitrate-free drinking water. You can also add that water to your tank, knowing that the membrane removes 92 percent of nitrates.[4]

It is worth noting that reverse osmosis cannot strip water of all its nitrates. If you prefer zero nitrates in your aquarium, you can compliment your reverse osmosis system with an additional nitrate removal tool or method. 

Keep in mind that your water’s nitrate concentration will influence the filtration system you purchase. Higher nitrate levels can make a reverse osmosis system less effective.

This is why it is so important to test the water beforehand. Give the results to an expert and ask them to recommend a fitting water filtration system.

A cleaning filter based on reverse osmosis.

2. Ion Exchange

Ion exchange is gaining momentum as an effective tool for removing contaminants from aquarium water.

One particular paper in Aquaculture Engineering emphasized the effectiveness of an ion exchange mechanism in removing ammonia from aquaculture systems.[5]

The paper’s data showed that the method could eliminate NH4+ if you forced water through an ion exchange resin. The study took note of the absence of nitrification, which explained the low nitrite and nitrate levels. 

Another 2009 paper (Nitrate Removal In Closed Marine Systems) identified the ion exchange membrane bioreactor concept as a reliable means of removing nitrates, proving once and for all that the ion exchange method works on nitrates.[6]

It can remove as much as 90 percent of the nitrates, possibly even more.[7] 

Like reverse osmosis, you can install a whole-house ion exchange system.[8] This ensures that your tap water is safe for human consumption and for use in aquariums. 

One notable alternative to reverse osmosis and ion exchange systems is distillation. People use distillation to remove contaminants from drinking water.

An ion exchange filtration system.

3. Water Change

Most aquarists use water changes to remove nitrates because they are easy to perform. It takes the average aquarist 10 or 20 minutes to complete a water change. 

But more importantly, they work. The act of taking out a portion of the water will also remove nitrates. 

Replacing the old water with new water will dilute the remaining nitrates. The more nitrates you have, the more significant the water change you need.

Although, most aquariums can keep nitrate levels under control with a 25 percent water change each week. You can escalate to 50 percent once nitrate levels reach 40ppm.

Technically, fish can tolerate nitrates as high as 50ppm, but 10ppm is the ideal concentration

A 50 percent water change is acceptable in an emergency. Fish don’t like large water changes because they cause significant alterations in the water’s chemistry.

Aquatic creatures appreciate stability. You can harm them by performing large or frequent water changes. A 50 percent water change is acceptable every once in a while, but not every day or even every week.

Use the water change to bring the nitrates down to acceptable levels before identifying and eliminating the factors that caused the nitrate concentration to spike. 

Once you eliminate those factors, you can transition back to smaller water changes of 10 to 25 percent.

Ammonia and nitrate spikes often require a drastic, 50 percent water change.

Does A Water Conditioner Remove Nitrates?

The term ‘Water Conditioner’ is quite broad. It refers to anything that removes toxins and contaminants. That includes water changes and reverse osmosis systems. 

If your focus is chemical products, some of them remove nitrates. You can find a water conditioner for every toxin that plagues an aquarium. 

Therefore, you should search specifically for nitrate removers. Pay attention to the packaging. If it doesn’t mention nitrates, it won’t remove the substance.

On the other hand, if it mentions nitrates, you can trust the product to combat the toxin by either turning the nitrates into nitrogen gas or binding the substance, neutralizing it, and allowing the bacteria in the biological filter to destroy it.[9]

If you don’t own one yet, I highly recommend getting the Seachem Prime Conditioner (link to Amazon). 

It will efficiently neutralize chlorine and chloramine and will improve the removal of nitrates, nitrites, and ammonia.

All you have to do is to add 1 cupful (5m/L) for every 50 gallons of water, and the product will take care of the rest. You can also use it as a preventive measure in a well-maintained tank.

What Is The Best Nitrate Remover For A Freshwater Tank?

It depends on what you want. A reverse osmosis system will do wonders for your aquarium. If you consult a professional, they can install a mechanism that filters your tank’s water.

However, reverse osmosis and nitrate-removing resins are somewhat complicated. At the very least, they are more likely to confuse beginners, which is why water changes are the best option.

Reverse osmosis and ion exchange systems can remove multiple contaminants. You can even soften the water. 

However, a water change is equally effective. The larger the water change, the more contaminants it will remove. You can even change 100 percent of the water if you prefer zero nitrates.

The ease of use makes water changes particularly appealing to newcomers because it takes 20 minutes or less to perform one.

Ultimately, your preference and resources will determine the nitrate removal method you will gravitate towards.

You can use a water testing kit to see whether the water conditioner worked.

Do Water Changes Always Remove Nitrates?

Even though routine water changes are an excellent option, in many cases, nitrates will remain high even when they are done properly.

That typically happens when the water source itself contains nitrates. It isn’t unheard of that some regions have high nitrate concentrations, even in tap water.

To overcome this issue, I typically suggest performing a test on the new water added to the fish tank. You can do that with any testing kit that checks for nitrates. 

The one that I usually use is the API FRESHWATER MASTER TEST KIT (link to Amazon). It is highly accurate and extremely cost-effective.

It is also possible that your tank is highly contaminated with rotten debris that releases ammonia, which later on, turns into nitrate.

That is why I encourage aquarists to vacuum the substrate each time they perform a water change or clean their tank.

You can easily do that with products like the Laifoo Aquarium Siphon Vacuum Cleaner (link to Amazon)

If you’ve never used such a device before, here is an excellent video that will walk you through that:

Pro tip: Dealing with ammonia is key when you find high nitrate levels in your tank. Here is an article with all the information you need about ammonia, including the specific products I use to remove it.

If you found this article helpful, these may also interest you:


The easiest way to get rid of nitrates is to perform a water change. That will actively remove some of the nitrates while diluting those that remain in the tank. 

It is also the cheapest option. You can also go with more advanced options such as reverse osmosis and ion exchange.

Those are typically implemented in the water system itself, freeing tap water from nitrates and other toxins.

If a water change didn’t fix your issue, you might have accidentally added nitrates from the water source itself. That is why checking the water beforehand is crucial.


  1. https://iopscience.iop.org/article/10.1088/1755-1315/920/1/012008
  2. https://www.merleswater.com/blog/bid/234656/removing-nitrates-from-drinking-water
  3. https://www.wrrc.hawaii.edu/research-projects/removal-of-nitrogenous-aquaculture-wastes-by-a-wind-powered-reverse-osmosis-system-year-2/
  4. https://www.freshwatersystems.com/blogs/blog/how-to-remove-nitrates-from-water
  5. https://www.sciencedirect.com/science/article/abs/pii/S0144860912000623
  6. https://pubmed.ncbi.nlm.nih.gov/19111983/
  7. https://www.wwdmag.com/contaminants/nitrate-removal-equipment/article/10917934/nitrate-removal-by-ion-exchange
  8. http://blog.watertech.com/nitrate-in-drinking-water/
  9. https://fishlab.com/nitrate/