What is a safe chlorine level for water changes?

[gaines]

As some of you know, I've recently build an automatic water change system involving a 500 cubic inch activated carbon chamber. I tested it and it showed no remaining chlorine (according to my test strips). It's been running for the past week for five minutes every six hours (I will try to calculate the actual water volume later this evening).

Now I'm testing the water to ensure that it continues sufficiently filtering chlorine and it seems to be showing .5ppm free chlorine. This brings me to the question of how much chlorine is damaging/lethal to fish.

If it's changing out 10 gallons of water at .5ppm, I'm guessing that means the tank ends up containing approximately .025ppm overall. This is an extremely rough guestimate as this would be assuming that the new water completely mixes.

Thoughts?

 

[gaines]

According to the Skeptical Aquarist, the level of chlorine in your average city water supply is not really worth worrying about in a partial water change.

Does this mean that any dechlorination that's taking place through my water change system is just a bonus and an extra safety measure as I'm changing out such small quantities at a time?

Frankly, if you have an aerator attached to your faucet, it may provide all the outgassing that's needed for a partial water change; after all, many people are using Python-type water-change hoses without trouble. And if the faucet aerator is charged with an activated carbon filter to improve the drinking water, so much the better! Fresh carbon will adsorb chlorine.

If you are impatient you could run an airline in the jug or can, but there isn't any reason to use de-chlorinator to neutralize chlorine (not chloramine), except in an emergency. Don't let anyone undermine your security about this fact. If you have any lingering doubts, borrow someone's chlorine test kit (don't buy one yourself) and test your water. Test the water that has passed through your faucet aerator. And test the water first from the tap and again after sitting still for twenty-four hours. If you insist on owning your very own chlorine test, by all means get it at the Swimming Pool Supplies section of your Home Depot. It's the very same test, using the very same chemicals, as ones that are specially packaged and specially priced for the "captive" aquarium market.

 

[TropicalNorth]

I've found doing 20% water changes with water straight from the tap (which is supposed to have a chlorine level of 1ppm) doesn't have any effect on the fish or bacteria. It dilutes throughout the tank and chlorine is very good at evaporating off quickly. I'm in the understanding bacteria die in concentrations at or over 1ppm.

You can run into problems however if your local water supplier decides to up the dose to 3ppm after heavy rains. This happened to my sister and as a result all the bacteria in the tank died and then all the fish died of ammonia poisoning. This is a pretty crap water supplier we're talking about though.

It's the bacteria you have to worry about with respect to chlorine and not so much the fish.

 

[gaines]

It's the bacteria you have to worry about with respect to chlorine and not so much the fish.

Excellent point about the bacteria. That's actually one reason why I ran my new water into the END of the sump after the sponges, polyfil, and ceramic rings. I didn't want any traces of chlorine going directly into my bacteria beds. As it stands, it really has to mix with at least 130 gallons of water and make it through the main tank before it gets to my primary biological filtration.

I'm considering looking into adding a mister as I've read it can be a great way to further remove chlorine by spraying the water in a fine mist. The main downside I see is that I would then need to build up some pressure before it would function, but I used standard household CPVC water pipe and made good connections so it should handle the pressure just fine.

 

[iresq]

Do you know if you have chlorine or chloromine? Chloromine in non-evaporative. Do you run activated charcoal in your reqular filters?

Is is possible to engineer in some kind of Prime injection?

 

[gaines]

Do you know if you have chlorine or chloromine?

According to our local water supplier, they do not use chloromine.

Do you run activated charcoal in your reqular filters?

Yes, but the quantities I use in my regular filter (the XP3 which is used as a return pump from the sump) is quite small compared to what the water goes through in the automatic water change system.

Is is possible to engineer in some kind of Prime injection?

I'm sure it would be possible to set up a dosing system of some sort, but I'd like to avoid having to go that route if I can sufficiently remove the chlorine through the carbon and aeration.

 

[Yoemen]

Just want to say in defense of the water supplier. They are required to up ammonia amounts after heavy rains to prevent any risk of contamination from run off or sewage. It is a very preventative measure, but it is required, just like shocking any well system with bleach after doing work on it.