Monday, March 3, 2014

Toxic Substances in Fish Tanks

Being a controlled environment, the artificial settings of fish tanks provide a favorable venue for the presence and accumulation of toxic substances. An aquarist is fully aware that fish keeping is a 24/7 responsibility. There are various factors that you have to constantly monitor including water quality, fish feeding and nutrition, overcrowding, presence of ammonia, heavy metals, etc to ensure that the environment inside the tank remains healthy and favorable to its inhabitants.

Poisoning is one of the most common causes of fish kills. Introduction and contamination of the aquarium environment with common toxins is very common. These toxins may come from the water, fish food, decorations, plants, and even the substrate. Toxins can also be formed as a product of metabolism or as a result of poor tank maintenance and management.

Among these potential sources of toxins, your water source is considered as one of the most important. You need to evaluate your source of water and the treatment process that it is subjected to before being distributed to the consumers.

Chlorine and Cholaramine Poisoning


Chlorine and chloramine, which are toxic to fish and other inhabitants of an aquarium, are commonly used to treat water. They can inhibit algal and bacterial growth along the water lines and make water potable and fit for human consumption.

Aside from a detectable chlorine odor emanating from the tank, fish which has been exposed to the toxin may be observed gasping for air which can eventually lead to suffocation and death if the condition inside the aquarium is not corrected as soon as possible.

First Aid Treatment: 

 Add a water conditioner since chlorine and/or chloramine exposure can kill all the fish in your aquarium within 24 hours.

Ammonia Poisoning


The presence of ammonia in aquarium water can be attributed to several factors including a new set-up, a change in the bio-load, a power outage, filter exchange, medications, and even the addition of new fish into the aquarium.

Fishes which have been exposed to ammonia are lethargic and usually seen hovering at the bottom of the aquarium tank. The gills are reddish to indicate internal and external bleeding that can eventually result in death.

First Aid Treatment: Aside from a water change, the water pH should be lowered to 7.0 or less. This can be accomplished by adding a pH adjuster to your aquarium water. A lower pH can convert ammonia into ammonium rendering it harmless and non-toxic.

Nitrite Poisoning


Fish exposure to high doses of nitrite over long periods of time can result in respiratory problems. As nitrite enters the bloodstream, it will bind with hemoglobin cells. These are the blood cells which are responsible in carrying and distributing oxygen throughout the body. As more and more hemoglobin bind with nitrite, it can result in suffocation of the fish.

First Aid Treatment: Add 1 teaspoon of aquarium salt per 300 gallons of water

Carbon Dioxide (CO2) Poisoning


The levels of carbon dioxide in a fish tank should not exceed 25-30 ppm. At higher levels, CO2 can cause poisoning that can lead to respiratory problems in fishes. Aside from rapid breathing, the affected fish is observed gasping for air and has a staggering swimming behavior. The most common causes of CO2 poisoning inside the aquarium tank include the malfunction of the CO2 reactor and the failure of the aquarium plants to efficiently absorb CO2 as a result of poor aquarium lighting.

First Aid Treatment: 

 Increase surface agitation and use air stones to aerate the tank and boost CO2 elimination from the aquarium water.

Hydrogen Sulfite


Hydrogen sulfite is formed when your aquarium tank lacks maintenance or there is a long power outage. The toxic compound is usually formed in the gravel substrate or within the aquarium filter.

Although relatively rare, the presence of hydrogen sulfite in the tank can be detected by a rotten egg smell that is present. As the toxic compound is absorbed in the body of the fish, it converts iron present in blood cells into sulfide which will eventually lead to fish suffocation and death.

Unlike other sources of toxins, prevention is very crucial to protect your tank inhabitants from hydrogen sulfite poisoning. The aquarium gravel should be thoroughly cleaned regularly. If there is a power outage, be sure to rinse out the aquarium filter before restarting to remove the toxins which are present in the filter.







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