I've got a 220L barrel set up for doing water changes on my 630L tank to pre-heat water and to let the chlorine evaporate, how long do I need to let the water sit (with an airstone running) before the chlorine goes away?

i believe it is 24hrs to be safe, but sunlight makes it go quicker

i believe it is 24hrs to be safe, but sunlight makes it go quicker

thats what ive heard also

By driving the chlorine off you are pushing the trichloramine through dichloramine and into monochloramine which is used in the USA to disinfect drinking water and is almost as toxic as chlorine.

Nice science lesson :-)

When filling your water drum try spraying the water rather than just allowing the hose to pour in. It helps the gasses to come out and if water is kept moving it also removes it faster. But I agree also at least 24hrs.

By driving the chlorine off you are pushing the trichloramine through dichloramine and into monochloramine which is used in the USA to disinfect drinking water and is almost as toxic as chlorine.

So letting it sit is really just a waste of time (aside from bringing it up to temperature)?

We can do straight water changes in Christchurch because there is no Chlorine added to the water. If I was using a chlorinated water supply I would be adding chemicals to neutralize the chlorine and other toxic chlorine componds which are formed when water is chlorinated as well as getting the water up to temperature. Why people are prepared to try and get rid of the chlorine but are happy to leave the other chlorine componds which are almost as toxic is beyond me. Or perhaps they were looking out the window during the science lesson.

Why people are prepared to try and get rid of the chlorine but are happy to leave the other chlorine componds which are almost as toxic is beyond me. Or perhaps they were looking out the window during the science lesson.

Or perhaps they just hated chemistry and preferred biology... :lol:

So, if I leave the water sitting in the barrel with an airstone running for a couple of days the chlorine will evaporate, but there will be other harmful chemicals left?

So mister science teacher dude, chemistry isn't really my thing, but is it correct that if the chlorine or Cl compound oxidises on organic compond/cell it will have bonded with what ever it has oxidised & it will be become stable.

So extrapolating from this, a big water change all in one hit will have a negative effect on the bacteria and the fish.

A continuous slow drip into the aquarium will see the Chlorine almost immediately used up by the large mass of organic material in the tank.

Therefore a continuous dripper system (which I use on my breeding tanks 2-4 litres/hr) will provide pretty stable conditions, with very little free chlorine zapping around causing damage?

No

Lol a spectacularly precise answer, any chance of further enlightenment?

Chlorine reacts with nitrogen and other compounds in the water to form amongst other things a group of compounds called chloramines. All water has a chlorine demand and it is the concentration of these compounds being formed that is the chlorine demand. All these reactions take place before free available chlorine is formed. When you swim in a pool and get sore eyes it is because the chlorine is used up and the chloramines are burning your eyes. This is fixed by adding more chlorine. The most reactive chloramine is monochloramine and this is used to disinfect drinking water in the United States. Add more chlorine and it goes to dichloramine. Add still more chlorine and it goes to trichloramine. When you have all trichloramine, add more chlorine and you get free available chlorine.

The same is true in reverse. Remove chlorine by aeration or whatever, and it all moves back to monochloramine which is almost as bad as chlorine.

You can get chemicals such as sodiom thiosulphate which you can add and they neutralize the chlorine and chloramines. You can buy these from the pet shop.

There endeth the chemistry lesson so have a good day.

The same is true in reverse. Remove chlorine by aeration or whatever, and it all moves back to monochloramine which is almost as bad as chlorine.

Does the same continue to happen in reverse, or does it stop at monochloramine?

So skip the chemistry lesson and tell me, am I wasting my time by letting the water sit with an air stone for any length of time? Should I just let it warm up (with out the airstone) and put it in the tank?

I remember talking to a well known goldfish breeder in Auckland a few years ago. I first met him as he was filling up display tanks at a conference. He was using a hose from the fire sprinkler system and the smell of chlorine was very strong. He then added his fancy (and very large) goldfishes straight to the water. When I asked him about removing the chlorine he said he never bothered since the water supply was chlorinated his fish would have to get used too it as he wasn't mucking about with time and expense getting rid of it. They were the biggest, healthiest goldfish I have ever seen!

As I said earlier. There is little point in removing the chlorine but not removing the chloramine which is just about as bad. The monochloramine will react with any other material in the water (like your eyes or the gills of a goldfish). I just think you should put your fish into disinfectant (chlorine and chloramines) or neutralize them all before you put your fish into disinfectant. the choice is yours realy---they are your fish. There seems to me little point in just removing the chlorine.

Out of curiosity, why not ring your waterworks engineer at the local Council and ask them what the chlorine demand of the water is. Councils usually aim to get about 2ppm FAC (free available chlorine) when they chlorinate the water supply. Generally they will have to add many times more than 2ppm to achieve that because of the chlorine reacting with the organics in the water. The difference is the chlorine demand and will end up mainly as chloramines.

The quality of the original water would have a big effect too I suspect.

If it's comiing out of a dodgy river and already has a high Nitrate level then the chlorine will have the effect that Alan is describing.

The water test that our local council provides has a Nitrate reading of ~0.25ppm for our tap water, so the level of chloramine formed would be pretty small. I dont bother with declorinator when I do water changes and my fish seem healthy.

If my tap water had a nitrate reading of 5 or 10 and that dodgy smell (chloramine?) then I would be using it for sure.

So it depends on the quality of YOUR local tap water.

Ian

Thanks guys, its interesting stuff, I will do some digging and see what comes up from the engineers at the council.

A lot of the problem is from organics in the water. Organics contain proteins which have amino acids hanging off them, also farm runnoff containing urea etc. You might be surprised what the chlorine demand is.

As I said earlier. There is little point in removing the chlorine but not removing the chloramine which is just about as bad. The monochloramine will react with any other material in the water (like your eyes or the gills of a goldfish). I just think you should put your fish into disinfectant (chlorine and chloramines) or neutralize them all before you put your fish into disinfectant. the choice is yours realy---they are your fish. There seems to me little point in just removing the chlorine.

So I take it that means that the monochloramine (or any chloramine?) will not evaporate? :-?

no