The best aquarium water conditioner ensures that the water you are using for the aquarium is safe for your fish.

It neutralizes the harmful chemical substances present in your tap water or seawater, which significantly affects the lifespan of your fish.

However, picking up a reliable fish water conditioner from hundreds of products available in the market can be confusing. To help you out, we have carried out extensive research and compiled a list of the best aquarium water conditioners that you can buy in 2021.

Comparison Chart

Product Bottle Size Suitable for Usage
Natural Rapport Aquarium Water Conditioner

16 fl oz Freshwater, seawater, and pond water 1-capful per 10 gallons
TankFirst Complete Aquarium Water Conditioner

16.9 fl oz Freshwater, seawater, and corals 1-capful per 10 gallons
API Stress Coat Water Conditioner

16 fl oz Freshwater 1-capful per 10 gallons
Seachem Prime Fresh and Saltwater Conditioner

16.9 fl oz Freshwater and seawater 1-capful per 50 gallons

Review Of Best Aquarium Water Conditioners

1. Natural Rapport Aquarium Water Conditioner


  • One-step application
  • Buffers pH and reduces stress
  • Adds electrolytes
  • Detoxifies heavy metals
  • This highly concentrated conditioner lasts for a long time


  • The water looks a bit cloudy after using the conditioner.

Natural rapport aquarium conditioner is a professional grade conditioner that has been the best seller in the market for more than two years. This is because it can neutralize harmful chemicals in both freshwater and seawater.

This all-in-one conditioner formula consists of 11 different ingredients that are harmless to your fish. It also removes harmful chemicals like ammonia, nitrate, chlorine with the help of a clarifier and de-chlorinator present in the conditioner’s formula.

This formula also helps balance the pH of your tank’s water without damaging the aquatic kin, and it also adds electrolytes in water and stimulates fish’s natural mucous coats. These slime coats repel parasites and bacteria from sticking on the fish’s scales.

It gets the name all-in-one as it eliminates the need for separate accessories, supplies, and chemical kits to treat water. Natural rapport has also proven safe for aqua live reefs, turtles, and fishes. This conditioner has proved effective and harmless to all marine pets, from beta fish to exotics.

Additionally, this conditioner is also effective in treating API stress coats. So by forming a synthetic slime coating reduces fish stress and heals its damaged tissues.


If you want an all-in-one water conditioner that can treat both freshwater and saltwater aquariums, then the Natural rapport aquarium water conditioner can be a great choice. It is effective, reasonably priced, and dissolves instantly.

2. TankFirst Complete Aquarium Water Conditioner


  • Safe and effective for all types of freshwater creatures
  • Clears cloudy water
  • No foul odor
  • One-step application
  • Lasts for a long time


  • Not very effective in treating nitrite

Did you know that your fish can smell? Imagine how much your tiny pets would suffer when a foul-smelling water conditioner is added into the tank. TankFirst conditioner solves this problem by using natural additives.

These additives cut the chlorine and chloramine particles present in your tank and also detoxifies ammonia. All this while still being odorless. Its cutting-edge formula provides a powerful conditioner that treats 20 gallons of tap water with just two capfuls.

You get a 16.9-ounce bottle, which you can treat up to 1,000 gallons of tap water. Even though a few drops are enough to treat water, small accidental spills won’t prove to be very deadly for your living creatures.

Also, this water conditioner has proven to deliver superior performance. It can act safely on freshwater and seawater creatures like live corals, shrimps, snails, and even on the most sensitive fishes, turtles, axolotls, and live planted aquariums.

Its unique odorless formula and fair pricing make it one of the best water conditioners for fish tanks. However, it lacks ingredients that can promote slime coat growth.


If the foul odor of the standard water conditioners bothers you, then we recommend you to try out the TankFirst water conditioner. It is safe, works fast, and, most importantly, has no foul smell.

3. API Stress Coat Water Conditioner


  • Provides a hospitable environment for fishes
  • Reduces fish stress by 40 percent
  • Affordable
  • Contains Aloe Vera extract
  • Controls and cures fish diseases


  • Aloe vera residue sticks to the tank.

Cheap products usually compromise with quality to justify their price tag. But some gems are not only affordable but of high quality. The API Stress Coat Water conditioner is proof of this statement. It is very efficient and affordable at the same time.

The API Stress Coat Water conditioner comes with a dual-action formula that aids in treating tap water. Thus it creates a safe environment for your tiny pet creatures. Also, it controls algae and bacterial growth and prevents fishes from developing diseases like ich and fin rot.

Fish’s protective coats get damaged when mishandled while shipping or fish fighting, and sometimes, they naturally shed it. This water conditioner is equipped with aloe vera extract, which boosts their coat regeneration speed to help them regrow their coat.

API suggests feeding your fish daily and testing the quality of water weekly. You can change 25 percent water every two weeks and while replacing the water, add this water conditioner to balance its pH and make it safe for your fish.

This water conditioner for fish tanks not only removes chlorine and chloramines from tap water but also neutralizes heavy metals and can be used for both saltwater and freshwater tanks.


API Stress Coat Aquarium Water conditioner’s unique feature that makes it stand out from the competition is its affordable pricing with zero compromises on the quality. So if you are looking for an affordable solution without compromising on the quality, then this might just be the right choice for you.

4. Seachem Prime Fresh and Saltwater Conditioner


  • Detoxifies ammonia
  • Biofilter removes the detoxified ammonia
  • It consists of a binder that renders ammonia, nitrite, and non-toxic.
  • Promotes the natural production and restoration of slime
  • Balances pH level


  • On the pricey side

Seachem is a renowned and globally trusted brand that has been making water conditioners for aquariums for over 30-year now. It has proven to be very effective and starts working straight away after being added.

It removes chlorine and chloramine from the water and detoxifies harmful elements like nitrite, ammonia, and heavy metals found in tap water. You can use it for both saltwater and freshwater tanks.

Its non-acidic nature neither disturbs the pH of the water nor over-activates skimmers. Also, this water conditioner contains aloe vera extracts that promote the natural production and restoration of slime coats. Besides fish, this fish water conditioner is proven to be harmless to aquarium plants and reefs as well.

Only one capful of Seachem Prime is sufficient to treat 50 gallons of water. It is entirely safe to use, so it won’t harm the fish if you spill a few extra drops.

Interestingly, you can safely increase the quantity of this fish tank water conditioner to increase the speed of slime coat replacement or fin regeneration. You can also double the dose to treating high chloramine concentrations.


This water conditioner for aquariums works in both freshwater and saltwater tanks. It’s safe, easy to use, and gives results instantly. So if you are looking for a complete concentrated conditioner that can remove chlorine and chloramine, then Seachem Prime can be your ideal choice.

Why Should You Use an Aquarium Water Conditioner?

Tap water and seawater consist of chemicals like ammonia, chlorine, nitrite, and hard metals. When you add this untreated tap water or seawater to your aquarium tank, it causes stress in fish, leading to death. Aquarium water treatment is necessary to avoid such situations. They neutralize these harmful chemicals and make the water safe for the aquarium.

Even though chlorine can escape from the water on its own, it takes around 24-48 hours to do so. When it happens, either the chlorine particles are exposed to a larger surface area, or air is bubbled through the water. But this 24-48 hour period is enough to impact the health of your fish negatively.

Not only that, but tap water is also treated with chloramine, which is non-volatile and doesn’t escape the water like chlorine.

This is why aquarium water conditioners are crucial for ensuring a safe environment for your tiny pets. In addition to the chemical removal, the fish water conditioner can also boost slime production in fishes and prevent diseases affecting the fishes.

How Much Water Conditioner Should You Use?

The quantity of the water conditioner that you should use entirely depends on the concentration of the product and the quantity of water. So make sure to check the bottle for instructions. Most conditioners are highly concentrated, and adding a few drops or a capful amount is enough to treat 20 gallons of water.

But there are a few highly concentrated conditioners that only require a few drops to treat large quantities of water. For example, the Seachem Prime water conditioner is highly concentrated, and adding 5 milliliters of it can treat up to 50 gallons of tap water.

So a single bottle will treat up to 5000 gallons of water. Likewise, this calculation varies from one brand to another.

Remember, you must only treat the amount of water you replace.

Frequently Asked Questions About Usage of Water Conditioner

– When Should You Use a Water Conditioner?

You should use a fish water conditioner on two occasions:

Whenever you are setting up a new aquarium, you should use a water conditioner to neutralize the pH level and make the water suitable for your fishes or when you are replacing your aquarium’s water.

– Can You Use Water Conditioners While Fish Are in the Tank?

It is not recommended to add water conditioners directly when fishes are in the tank. The best practice is to take the water to be treated in a bucket and add the conditioner to it. Make this mixture sit for some time.

By doing this, the water conditioner dilutes completely and treats your water thoroughly before it is put into the tank. But again, you can find some manufacturers suggesting you add their products straight into the aquarium water.

The problem here is that if this water conditioner is not mixed with the water quickly and your fish consume it, it can prove harmful. With highly concentrated conditioners, any small mistake like an accidental spill might compromise your tiny creature’s life.

If you are in a hurry and don’t want to go through the hassle of first treating the water in a bucket and then transferring it to your aquarium, then you can add the conditioner directly to your tank as well. However, you must make sure that you evenly spill it out throughout the tank and not drop it in one place.

– How Long Does It Take for Aquarium Water Conditioners to Work?

Most fish water conditioners can neutralize chlorine and chloramine instantly when added to water. However, to completely execute the fish water treatment process, it can take water conditioners anywhere from a few minutes to an hour. This is because they also need to detoxify harmful chemicals like ammonia, nitrate and remove them from water.

– How Does an Aquarium Water Conditioner Work?

When the chlorine present in tap water comes in contact with the fishes, it sticks to their gills and stops their oxygen supply. When the water conditioner is added to your aquarium’s water, its components form ionic bonds quickly.

This ionic bond acts like a magnet and attracts chlorine. So instead of chlorine sticking with the fish gills, it sticks to the water conditioner, making it completely safe.

– Are Water Conditioners Safe for Fish?

Yes, water conditioners are 100 percent safe for fish until they are used correctly. Each brand comes with its dosage guidelines, and you must make sure not to add excessive amounts of water conditioner to your tank. However, small accidental spills of conditioners don’t impact much on fish.

– Should You Use Water Conditioners That Only Treat Chlorine?

Some water conditioners can only treat chlorine and not the ammonia present in the fish tank. This ammonia is left untreated in the water, and it can kill your fish if it is accumulated. This problem is why it is recommended to use water conditioners that both treat chlorine and detoxify hard metals like ammonia.

– Are Water Conditioners Safe for Saltwater Tanks Too?

Water conditioners are completely safe to use with saltwater tanks. However, there is a passive downside to it too. Water conditioners do not remove chloramine and heavy metals from your tank. They just neutralize them.

Even though it makes the water safe for the fish, the neutralized chlorine can still act as a food source for algae and cyanobacteria in your saltwater tank, which will help them grow. To avoid this problem, we highly recommend you frequently change your tank’s water.

Check out our list of the best aquarium water changers to get the best water-changing system for your fish.

– What to Look for When Buying an Aquarium Water Conditioner?

Before paying for the best aquarium water conditioner, make sure to check whether the aquarium water conditioner:

  • Improve slime coat production: Fishes tend to either shed their slime coat when exposed to water irritants or do it naturally. Make sure to choose an aquarium fish conditioner that boosts slime coat production to prevent parasites from sticking to your fish’s scales.
  • Adds more electrolytes to water: A fish water conditioner formula that can add more electrolytes to the water is always a better choice. A high electrolyte level stimulates fish’s natural mucous coats; and makes them resistant to fungus, bacteria, and parasites.
  • Removes toxic chemicals: Many water conditioners only treat chlorine, which does not make the water completely safe. Make sure to purchase a water conditioner that not only removes chlorine but also detoxifies harmful chemicals like ammonia, nitrites, nitrates, and hard metals.
  • Other benefits: Other than removing the chemicals from water and neutralizing ammonia, water conditioners must maintain the pH level of your tank as well.
  • Has a low cost of usage: The quantity of conditioner used in treating certain gallons of water varies with different brands. It is always better to go for a more concentrated conditioner so that it lasts longer.


A fish water conditioner plays a crucial role in treating your aquarium water to make it safe for fish. It not only neutralizes the harmful chemicals present in seawater or tap water but also improves the health of your fish.

If you are still confused about which water conditioner among the list mentioned above is best for you, then we recommend you to go for Natural Rapport Aquarium Water Conditioner.

It is affordable, dissolves instantly, treats chemicals, and keeps your tiny creatures happy. It has the most positive customer feedback in the market, and you can never go wrong with it.

5/5 - (19 votes)


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