Chlorine

[Woody]

I'm wondering if anyone can post, for all of us, exactly what the danger of chlorine is, particularly in partial water changes of 20 percent or less. Reading through these forums, I see constant warnings to dechlorinate water, which I usually do—but I have to admit I sometimes forget when I'm just topping off a tank, and I've never had any apparent problems as a result. Obviously, I would never put fish in a full tank of chlorinated water.

I've always heard warnings about chlorine, but I've never heard what small amounts of it might do to my fish: Is it simply irritating to them or are small amounts a serious health threat? Is part of the concern that it kills beneficial bacteria?

 

[gadazobe]

Chlorine will slowly poison your fish as well as the good bacteria in your tank. It's not advisable to add water that still contains chlorine or chloramin to your tank. You're better off to add the dechlorinator and save your fish.

 

[Bol]

I'm not certain about the specific direct harm to the fish, but chlorine most definitely has the ability to kill bacteria. (Which is why it's used in swimming pools, and to treat tap water, in the first place).

 

[G_Sharky]

You might not have any problems at the moment, but if i keep on doing it your going to be facing some serious problems on your tank, so if I were you i'd make sure that's no.1 thing to remember when doing water changes....Fishy no like chloriny

 

[White Whale]

Chlorine will slowly poison your fish as well as the good bacteria in your tank. It's not advisable to add water that still contains chlorine or chloramin to your tank. You're better off to add the dechlorinator and save your fish.

Will chlorinated water also kill the bad bacteria (like Ich) along with the good bacteria?

 

[Bol]

Chlorine will also kill some "bad" bacteria, but ich is caused by a parasite.

I would doubt that chlorine would kill ich without also killing your fish and "good" bacteria.

 

[thecichlidaddict]

Chlorine stops oxygen from being absorbed by the fish - in effect they sufficate to death.

Chlorine is a very unstable chemical, and for many people, including myself, it has already dissapated completely by the time the water reaches the tank. This is probably the case with you. Nonetheless using dechlorinator is a precaution that should not be overlooked. You might be able to fill the tank once, twice, or fifty times without using dechlorinator, but one day if your city changes the formula used in the water you could end up with a disaster on your hands, and that is not worth the risk to me.

 

[bgraber]

Chlorine = Bleach.
Have you ever heard of "shocking" a swimming pool? Basically super-chlorinating it. If you swam in it then, you wouldn't be happy when you got out. With fish, a little bit would probably dissipate, or at least spread out to where it's not an immediate threat, but I'd equate chlorine in the water with wearing an itchy wool sweater. You just don't want to do that to yer fishies.. They can't tell you if they are slightly bothered by something.. It's up to you to take all the precautions you can.