The Ultimate Guide on Best Nitrate Remover for Freshwater Aquarium

Nitrate contamination is almost an inevitable part of any kind of aquarium. No matter what you do, nitrates will be produced eventually.

The root cause of this problem is the nitrogen cycle. The cycle starts with the creation of any waste. Such waste could be uneaten fish food, fish poop, dead plants or leaves, or any kind of other rotten particles.

Different bacteria then convert these wastes to ammonia – a toxin. In the second stage, again, such bacteria convert the ammonia to nitrite. Finally, these nitrites get converted to nitrates by some other types of bacteria.

Thus, the cycle continues.

The problem is that ammonia, nitrites, and nitrates are very toxic to the fish. If you can’t limit the contamination within the threshold point, your fish will fall victim to various diseases and can even die!

So, the easiest and the most obvious solution is to get the best nitrate remover for freshwater aquarium.

I have compiled a list of the best of the best nitrogen remover here with their perks and downsides. Moreover, I have added a detailed guide that would help you with every answer to all your questions related to nitrate contamination.

Product Name

Aquarium Size



​API Nitra-Zorb Filter Media Pouch

​Large (Up to 55 gallons)

​Instant Ocean Natural Nitrate Reducer Salt Water Conditioner

​All sizes

​Red Sea NO3:PO4-X Nitrate and Phosphate Reducer

​All sizes

​Seachem Denitrate

​All sizes

​Algone Aquarium Water Clarifier and Nitrate Remover

​All sizes (5 to 110 gallons)

Top 5 Best Nitrate Remover for Freshwater

API’s Nitra-Zorb is quite different from the nitrate removers you can find in the market. Rather than acting directly, you will have to use it as the filtration media in your already available filter.

So, technically, it’s an add-on that you will have to use alongside your filter.

Despite being an odd product, it is one of the most praised nitrate removers in the market.

Just place the pouch in the filtration chamber of your filter, and you are all set to go. You can see a drastic change in the nitrate level just within a couple of hours.

The only downside that I can think of is the larger than average size.

Notable Features

​- Uses synthetic ion exchanging resins

​- Clears off ALL the harmful elements of nitrogen cycle – ammonia, nitrites, and nitrates

​- Comes in a handy pouch design that is easy to use

​- Stops algae outbreak

​- Suitable for most of the Canister filters or other big filters

​- Rechargeable, so you can use one for a long time


  • ​Great at removing nitrates and other toxins
  • ​Easy to use
  • ​Easier maintenance
  • ​Longer than average product lifespan
  • ​Clears cloudy water


Among all the remover types, perhaps, the liquid type or the water conditioners are the most popular among the users.

While the API Nitra-Zorb is an add-on for the filters, this one is a stand-alone nitrate remover. You will not need a filter to use this product.

Just pour the solution (10mL for every 10-gallon water) into the aquarium and voila!

Instant Ocean is using its patented formula to impose a natural denitrification process. The solution has different types of helpful enzymes that react with the nitrate to produce nitrogen gas.

The downside is that its natural denitrification process is a bit slow. It might even take a month before you can expect results. Moreover, you will need to add the solutions every 3-4 days for about a month. So, the 250mL bottle might not be sufficient if you have a large aquarium.

Notable Features

​- Its patented formula invokes natural denitrification process, meaning it has fewer side effects

​- Converts the nitrates to nitrogen gas using enzymes

​- Creates a sustainable solution that ensures better water condition for a long time. Once the nitrate level an optimum level, it will remain so!

​- Zero maintenance; you will not have to change them, ever!

​- A stand-alone product; you don’t need to take any additional step

​- Has a time-release action that automatically enhances the buffering capability


  • ​Creates a better condition naturally
  • ​Offers a permanent solution
  • ​Brilliant performance
  • ​Zero maintenance
  • ​Easy to use


Yes, I haven’t said about the harms that phosphates can pose to your fish in this article yet. But let me assure you they are almost equally harmful compared to the nitrates.

Red Sea is offering a combined solution for both of the problems. So, that’ huge advantage of using this product as very few products in the market can do so.

Apart from that, you can say goodbye to the algae problem too.

Red Sea is a well-known brand coming from Israel, so you shouldn’t worry about the product being mediocre.

So, what are the negative traits of this product?

Well, I can think of the pungent odor of it, which pretty strong. Moreover, you must use protein skimmers if you are planning to use Red Sea NO3:PO4-X Nitrate and Phosphate Reducer.

Notable Features

​- Fights of both phosphates and nitrates as well as prevents the algae outbreak

​- Can reduce the nitrate level to zero

​- Comes from a well-known brand

​- Very easy to use; comes with different measuring cups to ensure proper dosage

​- Removes the phosphates naturally


  • ​Extremely effective
  • ​Reduces phosphates alongside nitrates
  • ​Budget-friendly
  • ​Positive brand value


  • ​Has a strong odor
  • ​Must be used alongside a protein skimmer
  • ​Overdosage can be extremely dangerous
  • 4. Seachem Denitrate – Natural Solution

Seachem Dendrite is a product suitable for those who don’t want to hammer through the nitrate contamination problem. It tries to enable a natural solution instead, which can be slower.

It tries to empower the biological filtration process.

If you are not having a severe nitrate contamination problem but want to create a naturally healthy environment, this should be your go-to choice.

It comes in a large bottle and only needs small portions every time you recharge.

Remember, it’s not a powerful remover but a slow and natural one.

Notable Features

​- Reduces all of nitrogen cycle trio – ammonia, nitrites, and nitrates

​- Ideal for both freshwater and marine water

​- Incorporates high porosity solid filtration elements

​- Enacts anaerobic denitrification process

​- Supports the existing biological filters by a great extent

​- A stand-alone product


  • ​Reduces nitrates and ammonia apart from nitrates
  • ​Safe yet effective
  • ​Reusable
  • ​Helps biological filtration
  • ​Doesn’t hamper the regular or natural systems of the aquarium


Algone is a well-known brand among fish keepers. This brand is often praised as a premium option that never fails to satisfy.

That being said, Algone Nitrate Remover is the most expensive option on my list today. Of course, there are some very logical reasons for the higher price tag.

First of all, it’s safe. It will not harm the fish or the aquatic plants in your aquarium. So, you can depend on it.

Then, it keeps the water cleanest compared to other nitrate removers in this list. And finally, it maintains a perfect dissolved oxygen balance in the tank.

The only negative trait that I can think of is the cost. If I neglected the pricing, it would have been the best nitrate remover for freshwater aquarium.

Notable Features

​- Fixes the “ugly tanks” by clearing the cloudy or green water and other particles

​- Safe for fish as well as the plants

​- Removes ammonia, nitrites, nitrates, and other organic and inorganic toxins

​- Suitable all kinds of water

​- Enhances bioavailability and microbial activities

​- Creates a chemical and biological balance while solving the nutrient imbalances


  • ​Offers best water quality; clears musky, green, or cloudy water
  • ​Safe to use
  • ​Removes almost every kind of pollutants
  • ​Creates a rich and balanced living condition for the fish
  • ​Superior quality


  • ​Very expensive

The Ultimate Guide on Nitrate Contamination in Freshwater Aquarium

What Are Nitrates and Where Do They Come From?

Chemically, nitrates are negative polyatomic ions that consist of one nitrogen and three oxygen ions.

Well, that is a difficult definition!

Simply speaking, nitrates are the by-product of waste, that mostly comes from ammonia in your aquarium. Different types of biological components in the fish tank rot over time and produce nitrates.

So, nitrates are not just another type of waste; they are rotten wastes!

Nitrates produce in your fish tank from a variety of sources, such as –

  •  – Extra fish food that is uneaten
  •  – Fish feces or poop
  •  – Rotten plants
  •  – Other forms of dirt, often coming from filters

So, now you now where nitrates come from. However, the actual production process of nitrates is a bit more complicated.

To understand that, you will have to review the nitrogen cycle in the fish tank once again.

​1. The first stage begins when ammonia gets produced. Various types of waste initially break down and produce ammonia.

​2. Then, a type of bacteria known as “Nitrosomonas” converts the ammonia into nitrites. Nitrite is another type of negative polyatomic ion that consists of one nitrogen and two oxygen atoms.

​3. Finally, another type of bacteria called “Nitrobacter” does the finishing job. Nitrobacter converts the nitrites to nitrates in the final stage of the nitrogen cycle.

So, the summary is somewhat like this –

Regular waste > ammonia > nitrites > nitrates

You might get confused thinking that nitr-ITE and nitr-ATE are the same component. In reality, they are very different!

First of all, nitrites tend to be extremely toxic, whereas nitrates are almost harmless (if the quantity is low). So, thanks to Nitrobacter!

Nevertheless, I must warn you that nitrate can cause very serious damage if the quantity exceeds a certain threshold.

Also, no matter what you do, you can never eliminate the nitrates from the fish tanks. All you can do is reduce the quantity so that it doesn’t pose a lethal threat.

What Is A Nitrate Remover for Freshwater?

Okay, it’s pretty clear that nitrates can cause serious harm to your freshwater fish. The simplest solution to that problem is to get a nitrate remover.

Such removers act as an equalizer that balances the level of nitrates, nitrites, and even ammonia.

I know you might be skeptical, but you shouldn’t worry about these removers to be harmful. These are quite reliable and safe to use in your freshwater aquarium.

Moreover, these nitrate removers also create a chemically friendly living condition for your precious fish.

Apart from removing the harmful substances, it also clears the water. I am sure the cloudy and dirty water don’t make your aquarium look good!

There are many other ways to remove the nitrates from water apart from using the nitrate removers. But this is the easiest and the most effective solution to the problem.

What Happens If Your Nitrate Levels Are Too High?

Let’s assume the worst-case scenario first. What if your aquarium is already heavily contaminated with nitrate?

No, not all of your fish will die right away!

Unless you have some sensitive breed or corals in your aquarium. In that case, increased nitrate levels might pose a lethal threat.

Although high nitrate contamination levels will not kill your fish, it will certainly create some other problems. Obviously, they would be living under excruciating stress.

Such stress will soon breed some nasty problems –

1. Unwanted Diseases

Nitrate contamination is the root cause of several diseases for fish. Some of the serious diseases that you should be aware of are Hemorrhagic Septicemia, Fin Rot, Hole-In-The-Head (Hexamitiasis), etc.

Well, the nitrates in the water don’t directly cause these diseases, but it creates an environment that invites harmful bacteria and parasites who directly cause them.

In some severe cases, these diseases can also pose a lethal threat.

2. Poor Growth Rate

If your fish is growing at a lower than average rate, you should check the nitrate level in the aquarium. The foul water is often the main culprit behind the slower growth rate for the fish.

Moreover, your fish might never reach the maximum size living in a nitrate-rich environment.

3. The Color Issue

Higher nitrate condition often is the main villain behind the cloudy or dirty water in the aquarium. If your fish continue to live in such water, soon, the color pigmentation cells get heavily damaged.

Soon, the rich, vibrant color of your fish will fade away. They might look dull and pale too.

4. Reproduction Will Take a Hit

Things are even tougher for you if you are trying to breed fish. A nitrate-rich water might damage the reproductive organs of your fish. They might even not feel interested in taking part in reproduction activities.

You must keep the nitrate level to a bare minimum level if you are a fish breeder.

5. Shorter Life Span

Nitrate contamination (low rate) might not kill off all your fish right away, but their life span will take a serious hit.

Fish living in a higher than average nitrate contamination don’t live as long as others living in a healthier condition. So, in a way, nitrates are killing your fish!

Therefore, it’s clear that a higher nitrate level in water extremely dangerous for the fish living in the aquarium. As a fish keeper, you must provide your fish with a better living condition free from higher nitrate contamination.

What Are the Right or Safe Nitrate Levels in Aquarium?

As you know already, you can never reduce the nitrate level to zero – it’s practically impossible.

So, what should be the tolerable level of nitrates?

In a general sense, the ideal level stands somewhere around 5 to 10 ppm.

Don’t worry, ppm (parts per million) and mg/L (milligram per liter) are equivalent and interchangeable units.

The answer depends on four critical factors –

1. Type of fish (freshwater/saltwater)

2. The Size of the tank

3. If and what kind of plants are in that tank

4. If there is any invertebrate (shrimps, crayfish, crabs, etc.) living in the tank

Depending on the tank type, you should always keep the nitrate level below the threshold limit. The following chart should help you –

​Freshwater Tanks

​General freshwater tanks​40 ppm
​Tanks with aquatic plants​​30 ppm
​Brackish / Saline​​50 ppm
​Pond​​50 ppm

On the other hand, in saltwater conditions, the nitrate level should be even less.

​Saltwater Tanks

​Coral tanks​0.25 ppm
​Reef tanks​1 ppm
​FOWLR (Fish Only with Live Rock) tanks​30 ppm

However, I should warn you that the above guide is a “general sense.” It would be better if you set the maximum nitrate threshold for individual species of fish that you are planning to have.

For example, bettas can sustain 10 to 20 ppm nitrate concentration.

If you are planning to set up a hospital tank, you should always keep the nitrate limit below 10 ppm despite the type of fish.

If you are truly struggling to maintain the nitrate level, I would suggest you use some nitrate consuming algae. Several algae might help you in this case.

How Do You Test for Nitrates?

There are several ways to measure the nitrate concentration in water, but the easiest way is using a colorimetric test kit.

Such test kits work for both salt and freshwater.

They work similarly compared to the pH test kits. But you should always check the instruction manual before you jump in.

There are a lot of good brands out there and should be available in your local pet shop or fish store. You can choose any one of them but always check the feedbacks and reviews before buying.

However, these test kits might give you a false alarm as the amines in the water interfere with the result.

So, beware!

How to Lower Nitrate Levels in Freshwater Aquarium?

Now you know how you can test the nitrate concentration and crosscheck it with the chart that I have mentioned above.

What if you see that the nitrate levels are off the chart?

The first step would be to stay calm. There are several things that you can do to reduce the level.

But I should tell again; you can never reduce the level to zero. So instead of thinking of any permanent solution, you should check periodically and follow the strategies below.

1. Change the Water

This the probably the most obvious solution. But changing water doesn’t mean that you should change the whole tank water at once. Rather, you should be changing a portion of water periodically.

Start with changing 20% of the water at a time every week.

It would instantly reduce nitrate contamination. However, nitrates are present in common tap water or other natural sources, i.e., pond water or river water.

So, before you change the water, check the nitrate level of that water too. If the concentration is low, you might use it.

Otherwise, you should use filtered drinking water that has gone through the reverse osmosis (RO) process.

So, the key takeaway is changing the water regularly that comes from a clean source.

2. Using Conditioners

Although I am saying water conditioner, this is basically a type of nitrate remover.

For example, Instant Ocean Natural Nitrate Reducer in the list above is a water conditioner.

How do they work?

These conditioners interact with the nitrates in the water and start chemical reactions. In most cases, they convert them to nitrogen gas. The gas then exits the tank in the form of air bubbles. Even Instant Ocean Natural Nitrate Reducer works in the same way.

However, not every water conditioner works in the same way.

Some conditioners bind the nitrates with positive ions converting them to harmless compounds so that they don’t pose a threat to the fish. Then, these compounds get filtered if there is a biological filter in the tank.

  • 3. Using Nitrate Filtration Media

Most of the biological filters can get rid of the toxic nitrites. So, that’s a relief! However, not all of them can filter out the nitrates – the process is a bit more complicated.

So, you should get additional filtration media that works both for nitrites and nitrates. It would be best if you can get a “bio-media.” These media use specific nitrate eating bacteria that can get the job done.

Apart from that, you can even find some nitrate filtration pads that work almost in the same way. One single nitrate pad will last for two to three months. So, that’s definitely a good bargain.

  • 4. Plants Are Your Best Friends

The best natural solution that I can think of is getting suitable plants. Plants naturally intake nitrates for their growth. So, using a plant might create a self-sustaining environment.

That’s why you might see natural algae outbreak if the nitrate level skyrockets.

But not every plant will utilize the nitrates at the same rate. Some plants’ nitrate intake rate is so low that you will not even see any noticeable change. Even, you might see high nitrates in a planted tank.

Don’t feel bad; some plants are perfect for the job.

However, you will have to plant then in the filter rather than in the tank. I will increase the nitrate reduction process to a great extent.

I would recommend you to plant Lucky Bamboo and Pothos. These plants are not only magnificently beautiful, but they would also reduce the nitrates. Their roots absorb the nitrates as food.

Strategies for Minimizing the Problem

All of the methods that I have just mentioned will help you reduce the nitrate. The good news is that there are some strategies that you can follow to fix the root cause.

Nitrate is the final product of the nitrogen cycle. The cycle starts with the waste that eventually turns to ammonia, nitrite, and then nitrate.

So, if you can minimize the waste, you might maintain the nitrate at a bare minimum level. Just like that proverb – prevention is better than cure!

However, you should get the best nitrate remover for freshwater aquarium.

Here are some tips that you can follow to minimize the waste in the fish tank –

​- Never give more than necessary food to your fish – it’ll turn to waste!

​- If you have plants in the tank, maintain them. Throw out the old leaves that will soon die, prune them often. If you see that the whole plant is about to die, snip them and throw them out! Think of it as gardening, but underwater.

​- Clean the aquarium regularly, get rid of the dirt and debris.

​- Clean the substrate layer often. Everything that is dead will end up here – like a graveyard! If you can, get a gravel vacuum cleaner to clean it off.

​- Keep the stocks at an optimum level. It’s never healthy to cramp up the aquarium. In most cases, higher nitrate condensation occurs due to this issue. Either buy a larger aquarium or multiple smaller ones.

How Does Nitrate Remover Work?

A nitrate remover performs a number of duties in the aquarium. Check them out –

​- Removes both soluble and insoluble pollutants

​- Eliminates ammonia, nitrites, nitrates, various proteins, and other organisms

​- Helps the growth of helpful bacteria and their colonies that eats the pollutants

​- Collaborates with other filtration elements like protein skimmer or filter to increase overall efficiency

​- Removes the cloudiness of water as well as the pungent odor

How Often Do You Use Nitrate Removers?

Generally, people and the fish keepers use the term “regularly” or “periodically” when it comes to the frequency of the usage of the nitrate removers in the aquarium.

It’s mainly because the term nitrate remover is generic. Different nitrate removers in the market come from different companies and brands. Each of them tends to be unique and has different chemical components in it.

So, there can never be a common guideline applicable to all the nitrate removers. The best strategy would be to follow the guideline specified with the products.

For example, API ZORB suggests recharging the tank with 80 grams of API ZORB every 5 days in case of nitrate contamination. On the other hand, you should use 10mL of Instant Ocean Natural Nitrate Reducer solution for every 10 gallons, 3-4 times a week, until you reach the desired nitrate level.

As you see, despite both of them being a nitrate remover, usage frequency varies.

Here are some valuable tips in this regard –

​- Never apply more than the recommended dosage. Otherwise, it would cause more harm than doing a favor.

​- Change the filtration pads regularly as per the recommendation from the manufacturers.

​- Stick to the exact guideline for nitrate removers specified by the companies.

What Are the Different Types of Nitrate Removers?

As I have mentioned before, different nitrate removers have different usage guidelines. It’s because there are several varieties available in the market.

Here is the basic classification –

Specially formulated to work against chloramines, chlorine, and heavy metals that also works against nitrates. They are suitable for both saltwater and freshwater fish.

  • 2. Nitrate Sponge

Being a sponge, it absorbs the ammonia directly. If the ammonia level reduces, the level of nitrites and nitrates will automatically reduce. Moreover, these sponges help the anaerobic bacteria to grow and create a balanced system.

  • 3. Nitrate Pads

These pads also reduce the nitrate level in the water. At the same time, it absorbs dirt, debris, excess food, and other foreign particles.

  • 4. Nitrate Tablets

These tablets dissolve in the water and eradicate the nitrates. They also help to increase the oxygen level in the water by breaking down the nitrates to nitrogen and oxygen. Some users have also reported that nitrate tablets also fight off the Brown Blood disease for fish.


In my opinion, API Nitra-Zorb Filter Media Pouch is the best nitrate remover for freshwater aquarium. It offers the fastest nitrate removal compared to others.

Then, Instant Ocean Natural Nitrate Reducer Salt Water Conditioner is clearly the runner-up being the only water conditioner and for sheer popularity.

I will give the third position to Red Sea NO3:PO4-X Nitrate and Phosphate Reducer – the budget champ!


  • William Rieder

    Hi, my name is William Rieder and I'm a pet and animal blogger. I love reviewing all things pet related, from dogs to cats to horses! I also write about other topics such as personal finance and relationships. I enjoy helping people find the perfect pet for their lifestyle and am always interested in hearing what they have to say about their pets.

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