Ammonia and nitrates are amongst the most deadly toxins present in aquarium water. These soluble chemical compounds, when allowed to accumulate, are highly toxic and are common causes of fish fatalities.

AMMONIA

Where does ammonia come from?

Ammonia is the primary by-product produced during a biological cycle through which waste products and decaying organic matter (dying animals and plants) are broken down.

Ammonia is a significant danger in newly set-up aquariums because the bacteria that would naturally decompose waste and decaying matter are not properly established yet. The problem worsens if a large number of fish are added at the same time, as the large amount of fish excrement produced will have adverse effects on the water quality.

How do they affect fishes’ health?

Excessive levels of ammonia can cause skin reddening and gill malfunctioning due to the caustic effect of the toxin on these surfaces. Fish suffering from ammonia poisoning tend to isolate themselves, lie on the tank bottom, clamp their fins and secrete excess slime, and are much more susceptible to parasitic and bacterial infection. If the problem is not rectified in time, the fish may die.

How should the accumulation of ammonia be prevented? 

This problem can be managed by: Installing a good filtration system, carrying out regular partial water changes, not overfeeding fish and overstocking the aquarium, quickly removing excess food, fish waste and any dying animals and plant parts from the water and using the appropriate water conditioners whenever necessary. 

Basically, what all this boils down to is due diligence in maintaining water quality.

NITRITE & NITRATE

In the above-mentioned biological cycle, ammonia is converted by bacterial action into nitrite, which is just as dangerous to fish.

In the next step of the cycle, nitrite is then converted to nitrate, a relatively safe compound, by another type of nitrifying bacteria.

It is therefore crucial that a new aquarium is properly “cycled” to allow enough colonies of nitrifying bacteria to be established before fish are introduced into it.

This “break-in” period is about two to four weeks. During this time, the ammonia level will drop while the nitrite level will quickly rise. This is known as a nitrite spike, which will take a few weeks to subside.

Nitrate is also an ingredient found in plant fertilisers. Generally, nitrate is not harmful to fish, so long as it is not present in excessive amounts.

In a properly maintained aquarium, there should be no measurable levels of ammonia and nitrite. If your fish become sick or you wish to check if your new aquarium is properly cycled, you can make use of test kits for measuring ammonia and nitrite levels to gauge if the water is safe, or too toxic for your fish.