POISONOUS SUBSTANCES IN AQUARIUM WATER
As we are all aware, atmospheric air is made up of about 23 per cent oxygen and 76 per cent Nitrogen, together with a host of other gases in very minute quantities. It follows that when we put on the air-flow system of our aquarium, the air pumped in contains a little oxygen and a lot of nitrogen.
This atmospheric nitrogen can be lethal to fish when the water is oversaturated (over 100 per cent saturation) with this gas.
Research has shown that nitrogen embolism, otherwise known as NITROGEN GAS BUBBLE DISEASE, can occur with 103-118 per cent nitrogen saturation and cause a lot of fish casualties.
This condition can affect an aquarium fish when one is replacing the old aquarium water with slightly warm fresh water. The infection is characterised by the presence of small bubbles of nitrogen beneath the skin, in the fins, tail, or mouth, behind the eyes, and in the blood vessels.
One can prevent the disease by aerating the water for a while in order to clear the excess nitrogen. Affected fish should be placed in a small bucket of water into which an air stone device has been passed to properly aerate the water. The fishes are bound to recover spontaneously if the aquarist takes immediate remedial action.
Apart from the Gas Bubble Disease (caused by atmospheric nitrogen), there are some other nitrogen compounds which produce poisonous substances; these are Ammonia, Nitrite and Nitrate. They are all formed by the breakdown of proteins, since they are produced in the aquarium itself, small quantities are always present in the water under normal conditions.
Ammonia (NH3) is the most important end product released during the digestion of protein by freshwater aquarium fishes; it is released in the form of ammonium (NH+4). Small quantities of ammonia are also produced during the breakdown of proteins present in the urine and faeces of fish and in food fragments. Both the ammonia and ammonium in the water are in balance according to the following chemical equation.
NH3 + H20 = NH4 + OH *NH4 + is not harmful to fish.
The balance depends on the acidity (PH) and temperature of the water. When the PH is low, together with a slight temperature, like in a natural aquarium set-up using a split in candescent bulb lighting system, the NH3 levels are low and NH4+ is high. The reverse is the case in an artificial aquarium set using a white gravel base together with a fluorescent lighting system. Here, the water is alkaline due to the increased calcium carbonate (CaCO3) released by the gravel, the resultant high PH (hydrogen-ion concentration), together with low temperature, usually result, in a high NH3 level which normally cause the popular Acute Ammonia Poisoning disease (AAPD) which is usually rampant among fishes kept in aquariums using a completely white gravel bed.
The disease could be cured by a breakdown (oxidation of the ammonia by Bacteria in the aquarium itself or, more effectively, by a biological (under-gravel) filter through the process called Nitrification, as shown below:
Ammonium (NH4+) Nitrite (No2) Nitrate (No3)
The end product, Nitrate, is 2,000 times less poisonous than nitrite and relatively harmless to fish.
Poisoning by Ammonia or Nitrite can be avoided by maintenance of good-quality aquarium water based on the natural system.
The interproduct, Nitrite, is also very poisonous to fish, because it oxidizes the red blood pigment (haemoglobin to methaemoglobin) to a compound that cannot transport oxygen, hence fish could suffocate.
The chemical chlorine (Cl₄) happens to be a powerful disinfectant which our water authorities add to our water supply.
Any freshly obtained tap water contains as much as 0.17mg/l of this chemical, which is not actually harmful to human beings but could be harmful to fish, since as little as 0.1mg/l is considered dangerous to fish survival.
The good news for aquarists on this chemical is the fact that once the water is obtained and left in a container, the chlorine releases itself from the body of the water completely within 48 hours. Hence, it is always advisable that you store your mains or tap water for about 2 days before use in an aquarium.
Alternatively, you could remove the chlorine from the water by passing it through activated charcoal in a side box filler or by gerating it vigorously for about 24 hours.
Failure to observe the above precautions could probably be the major cause of fish deaths that normally occur after the "servicing" of aquariums operating on an artificial system.
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