chlorine, nitrite, ammonia

[CoKen]

hi guys,

i have a question on chlorine, since chlorine exist in our tap water because it was added in to purify for human consumption, so it is a good. but why when come to fish tank water quality issue, chlorine need to be removed (de-chlorinated) before pouring into the tank? why fish can not live with purified water?

how about nitrite and ammonia? why do they exist in the tap water if they have side effect or bad to human health, at least bad to all fish.

your reply/answer is appricated.


rgds
Ken

[Alight]

Chlorine kills bacteria and protozoa by oxidizing them. Bacteria, unlike most chemical pollutants, can multiply and make you very sick or kill you, so it is very important that they not be present in water you drink. Likewise some protozoa. Both of these could grow in the water pipes that bring water to your house and in the pipes of your house. The chlorine in the lines added by the water company prevents this.

Chlorine does have a downside, in that it also combines with organic compounds in water (if there are some--which most water systems to have) and forms toxic compounds. Almost always, these compounds are found only in minute quantities that cannot directly make you sick or kill you in the short term. However, they can build up in your body and cause cancer if in high enough concentrations over long enough periods of time.

Many water companies are now adding ammonia to the chlorine in the form of chloramine because this substance is less reactive with organic compounds and produces fewer carcinogenic chlorinated compounds.

Remember, you are drinking this water, not breathing it, and the amount of water you drink at any one time is small compared to your body weight. Also, the water goes to your stomach that has large quantities of HCl (another great oxidizer) so the oxidating properties of the chlorine in the water is very small compared to your own stomach chemicals.

This isn't true for fish. The chlorinated water would have direct contact with their gills and would oxidize cells in these very important organs, causing them to not be able to exchange oxygen and carbon dioxide, effectively smothering the fish. This is why it must be removed.

Water companies do not add ammonia. (In fact water companies cannot have even very small amounts of ammonia in the water as it is considered a major pollutant). They add chloramine. However, to get rid of this stuff in the water for your fish tank, you have to break the stuff down to chlorine and ammonia. You can then remove the very poisonous chlorine by combining it with another chemical. The ammonia is then free in the water, but usually in quantities that are not toxic, and these days, many of the compounds used to treat the water bind the ammonia into a non-toxic form that can be broken down by your biofilter in your tank.

Nitrite should NOT be present in your tap water. If it is, your water company has a problem. Nitrites are very toxic. Nitrite is the result of bacteria action on ammonia, and in your fish tank, should be converted almost instantaneously to nitrate unless your tank is not cycled properly. Nitrate is not terribly toxic to mammals or fish, but in high quantities can cause problems in sensitive species, like Discus.

Nitrates may be present in your tap water, but not in high ammounts in the US as the EPA does not allow high concentrations. In the UK, higher ammounts are tolerated, probably because it is in most water sources and would be very expensive to remove. Trading off the health effects vs cost.

[Jeckel]

Nice explanation...thanks for taking the time to write it all down!

Jerry

[CoKen]

hi Alight

your explanation is very informative, thanks for that. you must be very good at chemistry. good on you. :)

rgds
Ken