How to Test Water In My Fish Tank?

If you just set up an aquarium, water testing is a critical part of your fishkeeping routine. Chemicals such as nitrite and ammonia build up fast in an aquarium to pose a great danger to the health of your fish.

Consequently, a test kit is a piece of important equipment that you must invest in if you want your venture to be a success.

However, if you lack the technical know-how on how to test the water in your aquarium or cannot afford a test kit, it is always good to procure affordable testing services from a shop near you.  Some of the shops charge a monthly fee while others offer free testing services to their clients.

Why Should you Test Aquarium Water?

An ideal aquarium requires top-notch water quality upkeep that protects fish and plants from the harmful effects of chemical build-ups.

When you test your tank consistently, you prevent the buildup of toxins that could pose severe dangers to your investments. The following are some of the key reasons why you should test the water in your aquarium:

– Testing prevents fish deaths

If you allow chemicals such as ammonia to build up to critical levels, it could harm your fish. Water that is not tested regularly leaves your fish sickly. The ammonia, which is a byproduct of fish waste, is very toxic.

When fish consume the chemical in high levels, it may result in their death. Typical symptoms of ammonia poisoning include sudden death in fish, fish that gasps for air at the bottom, fish that lies at the bottom of the tank, and a red circle in the gills of the fish.

– Prevention of algae growth

If you want water that is clear for the optimal health and growth of your fish, you should consider consistent testing. Murky and greenish water is not good for your fish. A high presence of algae usually causes greenish matter in water.

Algae increases when water is subjected to light and will cause a lot of nuisance and irritation to your fish. Regular testing ensures that you nip this problem in the bud before it spreads over that tank.

– Testing Prevents chlorine poisoning.

If you are using tap water in your aquarium, then you need to do regular testing. Tap water contains a high level of chlorine. Although these chemicals are safe for human consumption, it could spell trouble when you use it in your fish tank.

If you notice any presence of chlorine in the water, treat it with a suitable de-chlorinator. Ensure the chlorine level is maintained at zero. Some of the symptoms of chlorine poisoning include distress fish, gills with a whitish tinge, and irrational quick and jerky movements in fish.

– Suitable PH level

You must maintain an ideal PH level in your tank. The only way to be sure of the PH level is by testing the water. The right PH level for your tank should range from 6.8 to 7.6. However, some fish need a higher or lower PH level.

Therefore, it is important to check the appropriate PH level for the species of fish you are keeping. To maintain a good PH level, you need to change the water in your tank regularly. Breakdown of organic materials usually degrades the water level over time.

 What Water Parameters to Test?

There are many different parameters you can test in your aquarium. Below, you will find an overview of each water parameter and their importance as well:

– Ammonia

Ammonia in water is a result of fish waste. Ammonia is harmful to fish, and the only safe level is zero. In most cases, a newly set up aquarium contains high levels of ammonia because of the absence of a nitrifying bacteria.

Ammonia could also rise to alarming levels if you add new fish to the aquarium fast. If you want your fish to be safe, continually test your water for ammonia.

– Nitrite

There is a correlation between the presence of ammonia in your tank and the presence of nitrite. Typically, a rise in nitrite levels results in a spike in ammonia. Nitrite can harm your fish.

It causes your fish to suffocate by inhibiting its oxygen exchange in their bloodstreams. If you notice your fish breathing fast or gasping for air at the surface, they could be experiencing the toxicity that comes with high levels of nitrate chemicals.

– Nitrate

Nitrate is another chemical that you need to test in your tank. Although it poses less danger to your fish, high levels of nitrate will cause your fish to experience stunted growth. It also weakens their immune system.

– pH

You should also test the pH levels in your aquarium to ensure that the right level is maintained. Most tropical fish grows healthy in pH levels of between 6.8 to 7.1

– Water hardness

Extreme hard or soft water can pose dangers to some species of exotic fish.  If you are keeping some popular exotic fish, it is crucial to carry out water tests to determine the right hardness levels that are ideal for the healthy growth of the fish.


Typically, TDS refers to the total dissolved solids found in water. TDS is a combined measure of the organic and inorganic material found in molecular form in your tank.

High levels of TDS results in reduced photosynthesis in plants. It also reduces water clarity and increases water temperatures to dangerous levels. Most aquatic animals can live well in waters of TDS between 300 and 400.

– Alkalinity

Alkalinity refers to carbon hardness in the water. Typically, the presence of carbon in water helps stabilize the water PH levels.

When you change the water regularly, carbon levels are greatly reduced. You, therefore, need to do carbon tests to ensure that the water has the right levels.

– Phosphate

Typically, high levels of phosphates in a fish tank come from decaying organic material. Other sources of this chemical include tap water and water additives. Although phosphate doesn’t present any risks to your fish, it triggers and encourages algae growth.

– CO2 Level

 You need to conduct weekly CO2 tests if your aquarium has a high population of aquatic plants. High levels of carbon dioxide are dangerous to your fish. It will reduce the ability of the fish to transport oxygen in their blood and cause them to suffocate.


The prevention of excess chemicals in your aquarium should be your top priority.  You need to adopt an excellent fish keeping routine that involves a lot of water testing if you want the fish to be healthy and achieve ultimate growth. The tips provided in this article will give you a good starting point for water testing.

Fishkeeping   Updated: November 5, 2020
avatar Hey, I'm Fabian, chief editor at Aquarium Nexus. I really enjoy the aquarium hobby and love sharing my experience with others. If you have any questions feel free to contact me or leave a comment below.

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