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Water Chemistry

Water Chemistry

You’ve got everything in place, an aquarium, the filtering equipment, some aquatic plants, and sand. You landscape the aquarium and set it up how you envisioned it.  You add water and everything looks just like how you imagined it. Well, almost. Now that the aquarium is set, it’s time to introduce your pet to its new home.

Before you do that, did you check the vital element in which your pet is going to live? Well, what could be so critical? In case you are still wondering, we are referring to the water. Just as the air we breathe and the environment that we live in are critical for us humans, so is the water for your pet, and it forms the bulk of its environment.

Your aquarium is a living-breathing, contained environment and you will have to manage the processes that occur within it. Well, some of it at least. It’s not as hard as it seems though. You can follow a few steps and the environment should take care of itself. However, if you are facing some issues, do not worry, contact the experts for help.

Are water parameters that important?

Yes, it’s important to remember that while in nature, wastes such as dead and decaying matter, excreta, etc. undergo a natural decomposition. This may not be true in a contained environment such as an aquarium. If sufficient plants and bacteria are not present, the nitrogen cycle that normally exists, gets affected, and water may become very toxic for fish to survive.

What measures can I take to ensure the water remains clean?

Generally, the larger the aquarium, the lesser is the chance of the water getting contaminated. Excessive food wastage or fish excreta increase the levels of ammonia and nitrates. These are generally removed through the filtration process and aquatic plants. The substrate of the aquarium should be properly equipped to absorb the decaying matter and other chemicals, thereby keeping the fish safe.

Tap water should ideally not be used to fill up aquariums, mainly due to the chlorine content. In case tap water is your only source, you can use solutions that remove chlorine, and other impurities or consult with the experts. Excessive feeding and a large number of fishes can upset the water parameters.

How do I know the aquarium water is balanced and suitable for aquatic life?

In aquariums, the nitrogen cycle is maintained by bacteria, so a newly set up aquarium with a filter will not have sufficient bacteria to cycle nitrogen. In other words, the water in the aquarium should be healthy and balanced to suit the fish needs. To ensure the water balance is maintained, the water needs to be tested and changed periodically.

What parameters should I look for and how do I test the water?

Sl No.



Effects / Indicates


Nitrate content

< 40 ppm in freshwater

< 0 ppm in saltwater

Higher levels of nitrate increase fish stress levels and contaminate the water.


Nitrite content

0.5 ppm to 0 in freshwater and saltwater

Higher levels indicate that the filter is not working properly or the absence of nitrifying bacteria. This can contaminate aquariums, increase stress in fish and cause death.


Water Hardness

50 to 150 ppm depending on fish species

Indicative of the calcium and magnesium levels in water. Suitable values vary as per the fish species.


Chlorine Levels

0 ppm

Chlorine and Chloramine are found in tap water and not natural water bodies. These are to be removed from the water, before use.


Alkalinity level

Over 80ppm for freshwater and over 180 ppm for saltwater

Indicates the presence of carbonates, which act as buffer solutions. Lower alkalinity levels indicate a lower pH balance and an acidic environment for the fish. 



6.8 to 7.8 for freshwater

7.8 to 8.4 for saltwater

Indicates whether the water is acidic or alkaline. 7 indicates a neutral level. Changes in pH levels can unsettle the fish and increase stress.


Is water temperature important too? I don’t use a heating element in my aquarium.

Water temperature is also an important parameter. Adhesive temperature strips applied to the glass faces of the aquarium can be used to check readings periodically.  Ensure that the aquarium is not exposed to direct sunlight, it can cause increase in water temperature and promote algae growth. Aquarium temperatures are to be maintained constant so avoid keeping them near heat or light sources. Use heaters only if necessary and monitor temperature periodically. Let them be the recommended values based on the aquarium size and type of fish. Temperatures between 72° F - 80° F work best for tropical fish.