A green beautiful planted tropical freshwater aquarium with fish

Best Fish Tank Chemicals for a Thriving Aquarium

As a fishkeeper, you may want the enjoyment of seeing colorful tropical fish swim gracefully before your eyes. But if you’re interested in fishkeeping, you may not realize that having an aquarium also involves biochemistry.

To keep fish healthy, it’s important to have aquarium water with the right chemistry. When keeping an aquarium, there are certain water parameters that you need to maintain for your fish to thrive. These parameters include the following:

  • pH
  • Chlorine
  • Ammonia
  • Nitrates
  • Nitrites
  • Water hardness

Fortunately, maintaining these water parameters has been made easier over time, with many products available nowadays to keep your fish happy. With these products come many questions, however. As I have years of experience with my own collection of fish and aquariums and experience as an ex-zookeeper, I’ll help you figure out which products you need, how to use them correctly, and which products are the best for your aquarium.

The Role of Fish Tank Chemicals

Chemicals play a big role in maintaining a safe and healthy environment for fish. The smaller the aquarium, the more unstable its water conditions will be, as smaller volumes of water are less able to absorb changes in water conditions. Aquarium chemicals are used to help stabilize these conditions.

Our Top Recommended Chemical Products

07/19/2024 02:22 am GMT

The following are the most commonly used chemicals used in aquariums:

Water Conditioners

Water conditioners are a general term for a variety of fish tank chemicals. These chemicals include:


Chlorine is a chemical that’s commonly used by water management districts. They add chlorine to your water to eliminate bacteria and other pathogens.  

Chlorine is toxic to fish, so it must be removed from the water before adding the fish. As a kid, I was taught to get rid of chlorine by letting the water sit for 24 hours before adding the fish. Otherwise, you can de-chlorinating chemicals to get rid of chlorine, fast.

I recommend MICROBE-LIFT Dechlorinator Plus as a dechlorinator.

The preferred level of chlorine for freshwater and saltwater aquariums is 0 ppm.

Chloramine Neutralizers

In some cases, chloramine will be used instead of chlorine, which is also toxic to fish. And while it’s true that letting water sit will remove chlorine, that’s not true with chloramine.  Chloramine will remain unaffected.

While not all de-chlorinators neutralize chloramine, other water conditioners do neutralize chloramine. One way to neutralize chloramine is to use an ammonia neutralizer.

The preferred level of chloramine for freshwater and saltwater aquariums is 0 ppm.

Ammonia Neutralizer

Ammonia neutralizers make water safe for fish and aquatic plants by neutralizing chloramine and ammonia. It’s important to understand that ammonia is what beneficial bacteria eat. If you don’t have enough beneficial bacteria, your ammonia levels may increase to toxic levels.

I recommend the MICROBE-LIFT Ammonia Remover as an ammonia and chloramine neutralizer.

Complete Water Conditioners

To save money and time, I recommend getting a complete water conditioner. A complete water conditioner will do the following:

  • Neutralize chlorine and chloramine.
  • Detoxify ammonia, nitrates, and nitrites.
  • Be safe for fish, invertebrates, and plants.

 I recommend the Seachem Prime Fresh and Saltwater Conditioner.

Reverse Osmosis Water Conditioner

Reverse osmosis water conditioners are mainly intended for freshwater aquariums with life plants. This water conditioner is used to restore the mineral and electrolyte balance of the aquarium. It also acts as a buffer, so it will help stabilize the water’s pH and GH. (More on this below).

My favourite reverse osmosis water conditioner is the Brightwell Aquatics Remineraliz.

Freshwater fish tank

pH Balancing Chemicals

Water has free hydrogen ions in it. The more free hydrogen ions water has, the more acidic it will be. The less free hydrogen ions water has, the more alkaline it will be. pH is a measure of the acidity or alkalinity of the water.

pH is measured on a scale of 0-14. The closer 0 the pH is, the more acidic the water will be. The closer to 14 the water is, the more alkaline it will be. A pH of 7 means the water is neutral.  

Adjusting the pH

You can test the pH of your aquarium by purchasing a pH kit. There are also pH-balancing chemicals to adjust the pH in your tank. Most freshwater fish like to have a pH near the neutral range. Saltwater fish can take a higher pH.

pH Range6.8 to 7.87.8 to 8.4

If you need to adjust the pH, it must be done when no fish are in the water. Suddenly changing the pH can cause your fish to go in shock. Though there are pH-maintaining chemicals you can use to adjust the pH, I recommend that you first try some natural methods:

To lower the pH:

  • Use deionized water or a reverse osmosis (RO) system.
  • Use peat moss or peat pellets in your filter. These items should be placed in a mesh bag to keep them contained.

 To raise the pH:

  • Place calcium carbonate-based items in your tank. Good sources of calcium carbonate include limestone, crushed coral, or dolomite gravel.

🐠 Make sure your aquatic ecosystem remains clean and healthy with our ultimate guide to aquarium maintenance.

Water Hardness Solutions

Water hardness refers to the amount of minerals dissolved in the water. There are two kinds of water hardness: KH and GH.


KH refers to how much carbonate is in the water. It’s measured using the unit dKH. KH acts as a buffer. The higher the KH, the more stable your pH will be. For this reason, having a high KH level is important for the health of fish and plants.


GH refers to how much calcium and magnesium are in the water. GH is also known as general water hardness and is measured using the unit dGH. The right GH levels are important for keeping fish and aquatic plants healthy.

Depending on the fish species, the preferred water hardness for a freshwater aquarium is between .50 to 150 ppm.

Fortunately, most fish can tolerate hard water. The few exceptions include wild-caught discus fish. If you need to increase the hardness of your water, you can add crushed oyster shells or buffer additives. Also, water hardness test kits are available on the market.

🐠 We’ve rounded up our top aquarium care products for a thriving fish tank. Check them out here.

Water Clarifier

Water clarifiers treat cloudy water and shouldn’t be confused with water conditioners. 

Water conditioners remove harmful elements from aquarium water, such as chlorine and chloramine.

Water clarifies work by causing particulates to clump together. The particulates in the water cause the water to be cloudy. When the particulates clump together, your aquarium’s filtration system can more easily collect them.

I recommend Aquatic Experts KloudAway Freshwater Aquarium Water Clarifier.

Beneficial Bacteria

Why are bacteria listed in an article on chemicals for fish? This is because beneficial bacteria are vital in keeping certain water parameters in check.

Like other living things, fish eliminate waste. The fish’s waste contains ammonia and nitrites, which are toxic. In their natural habitat, fish do not have to worry about these compounds because they normally live in large bodies of water, like the ocean or lakes.

Because of the large volume of water, ammonia and nitrites are of little consequence to fish. Also, beneficial bacteria in the water convert ammonia and nitrates to less toxic compounds, like nitrates.

When you have an aquarium, however, the volume of water is much less than an ocean or lake. Also, there may be less beneficial bacteria in the tank. Because of this, the ammonia and nitrate levels can climb to toxic levels.

This is why you need beneficial bacteria. Before adding an ammonia neutralizer, I recommend adding beneficial bacteria, like the Fritz Aquatics Nitrifying Bacteria to help maintain ammonia levels.

Non-chemical Solutions to Maintain Beneficial Bacteria

You don’t need to purchase beneficial bacteria if you set up your aquarium properly.  Remember the following:

  • The larger your aquarium, the better your fish can cope with ammonia, nitrites, and nitrates.
  • Make sure that you cycle your tank before you add your fish.
  • Provide your tank with a good filtration system.
  • Do partial water changes weekly.

Ideal Ammonia, Nitrate, and Nitrite Levels

You can purchase kits to measure your tank’s ammonia, nitrates, and nitrites levels. If needed, you can purchase beneficial bacteria.

Preferred ppm (Freshwater & Saltwater)Ideal ppm (Freshwater & Saltwater)
Ammonia≤ 02 ppm≤ 02 ppm
Nitrates< 40 ppm0 ppm
Nitrites< 0.5 ppm0 ppm
Freshwater fish tank

Risks and Precautions

Before you use chemicals in your aquarium, it’s important to read the brand’s instructions. I also encourage you to do your research. Let’s use dechlorinators as an example. When used as instructed, de-chlorinators are safe for fish, but there are exceptions.

The agents found in de-chlorinators require oxygen to neutralize chlorine. If the water in your tank is not properly oxygenated, adding a de-chlorinator could worsen the situation.  There will be even less oxygen for your fish and the beneficial bacteria.

You can minimize this risk by increasing the surface agitation of your tank. You can do that by using an air stone.

Go Natural

I recommend that whenever you can, go natural. Anytime you use a chemical in your tank, there’s a risk to your fish. If you follow the brand’s instructions, the risk is small, but the risk is there. By taking proper care of your aquarium, you will reduce the risks of using chemicals.

The following are tips for proper tank care:

Cycle Your Tank

When you set up your fish tank, let it cycle before adding the fish. To cycle your tank, add a source of ammonia to your tank like fish food. The fish food will cause bacteria to grow, which will convert the ammonia into nitrates.

Let the tank sit for several weeks for the bacteria to become established.

Do Partial Water Changes

I recommend that you do a 10-15% water change weekly. In other words, remove 10-15% of the water and replace it with fresh water. If your tank is well populated with fish, I recommend a 25% water change. In addition, I recommend that you vacuum the substrate.

Do Not Overfeed

Overfeeding your fish will cause the ammonia, nitrites, and nitrates to increase. Fish should only be fed once or twice a day. When feeding, do not feed more than they can consume in five minutes. Also, remove any uneaten from the tank.


 What is the best chemical to clean a fish tank with?

The safest aquarium cleaner is vinegar or a cleaning product designed for aquarium use.

What chemicals can I add to tap water to make it safe for fish?

 Use a complete water conditioner that neutralizes chlorine, chloramine, and ammonia.

How do I stabilize my fish tank water?

Follow the suggestions in this article to meet the water parameters of your aquarium.  When they are reached, you can maintain the stability of the water by doing a partial water change every two weeks. Also, test the water parameters regularly.

Can you put tap water in a fish tank?

Most municipalities treat their water with chlorine, chloramine, and other chemicals to kill bacteria and pathogens. As these chemicals are toxic to fish, you must treat tap water before adding fish. Using a water conditioner can help neutralize these chemicals. You can also use well water.


Chemicals are often needed to provide a safe environment for your fish; however, you can also overdo it. Properly maintaining your aquarium is the best way to reduce your need to use chemicals. We welcome your comments below, and please be sure to share this article if you found it helpful.

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *