Dechlorinator after or before pouring water? What do you do?

[HenryC]

I always find conflicting inputs on this one, so I would love to ask you guys, what do you do when you water chage:

Do you pre-treat the water with dechlorinator before placing it in the tank...
or
Do you dose dechlorinator straight to the aquarium, then pour new water in?

Some will tell you you will kill your fish and benefical bacteria the moment you pour new water in the tank, as the dechlorinator takes some time to neutralize it, others have told me they been doing it for ages with zero issues, they claim the chlorine concentration is so low that I won't do any harm (they argue that if the chlorine in tap water was so potent as to instantly kill your cycle and fish, we would be using tap water to disinfect wounds).

I personally pre-treat before pouring new water in cause I fear for my fish safety. but as I get bigger and bigger aquariums, it seems that pouring dechlorinator to the aquarium then using the hose to fill it up is going to be miles ahead in terms of convenience, but I do not wanna shock my fish.

What do you do?

Edited September 9, 2020 by HenryC

[StephenP2003]

58 minutes ago, HenryC said:

I always find conflicting inputs on this one, so I would love to ask you guys, what do you do when you water chage:

Do you pre-treat the water with dechlorinator before placing it in the tank...
or
Do you dose dechlorinator straight to the aquarium, then pour new water in?

Some will tell you you will kill your fish and benefical bacteria the moment you pour new water in the tank, as the dechlorinator takes some time to neutralize it, others have told me they been doing it for ages with zero issues, they claim the chlorine concentration is so low that I won't do any harm (they argue that if the chlorine in tap water was so potent as to instantly kill your cycle and fish, we would be using tap water to disinfect wounds).

I personally pre-treat before pouring new water in cause I fear for my fish safety. but as I get bigger and bigger aquariums, it seems that pouring dechlorinator to the aquarium then using the hose to fill it up is going to be miles ahead in terms of convenience, but I do not wanna shock my fish.

What do you do?

I use the python system straight from the tap. I usually do 50% water changes, and I add a full tank's worth of prime right before or during the fill-up. I've never had any problems. My tap water, according to my city's quality report, has as much as 2.2 ppm chloramines.

Edited September 9, 2020 by StephenP2003

[Sykes]

I've done both methods in the past and never had a problem with either. If I'm using 100% tap water, I'll typically just dose Prime to the full tank volume and add directly to the tank first. For added caution, I typically pour it in roughly the same spot that I'll be adding the new water (via Python) so that the current of the new water forces it to mix. I've done 50%+ water changes this way on a 125 g without issue, although I've since upped my plant game so large changes like that aren't necessary any more.

[James V.]

I almost always pour prime into my tank, then use a python strait from the tap into my tank.

i haven’t had any problems that I know of that came from doing this, and my fish don’t seem to care how I do it lol.

[ForestJenn]

When using buckets, I added dechlorinator to each bucket.  I've been using a python for the last few months so add dechlorinator just before flipping the switch to start the flow.  So far so good. 

[Dawn Dare]

Hello Henry. 
  Yes I understand why you have a question...  How I resolved this for my own peace of mind. Is using my trusty Python No Spill system and a “high sided flexible tote” Walmart, I place a pond pump inside the tote, add the measured amount of dechlorinator to the tote, an amount needed for the whole volume of water in my tank. Put the Python in the tote fill it. Doing my best to match the temp. Attached to the output of the pump, same sized tubing and a hook, (Also from Python) to hang on the tank to fill the tank. (Getting that hook is worth it.)
Wa lah!

It’s really a lot easier to do than to type about it. That way I know for sure that the water pumping into my tank has no chlorine. I don’t trust the tap water. I wish that I had room for a large RO system.  Only my nano tanks get that.

Best of luck to you. 
 

Dawn

[HenryC]

Hmm I'm surprised! Quite a lot of people just pour straight to the tank! Chlorine might not have a concentration that harmful then? Or the conditioners act pretty much instantaneously?

[ForestJenn]

2 hours ago, HenryC said:

Or the conditioners act pretty much instantaneously?

That was my assumption, but you made me curious.  Google says that it takes anywhere from 2 to 5 minutes. 

I watched a video of a gentleman demonstrating how quickly hydrogen peroxide reacted with a purple solution.  (Reaction cleared the purple in the water) in 200 liters of water.  The water cleared in about a minute while he mixed with his hand.  It seemed like a reasonable demonstration, but I'm not a chemist.  

I think the question boils down to how much exposure the fish get during a partial water change.  Something to consider.

[FishObsessed]

I love this question! It does seem much simpler to add the dechlorinator to the tank first. I might need to look into getting a Python lol. I use the bucket method....2.5 gallons at a time, but I have a mid size tank, not a large one. One of my dechlorinators says it "works in seconds"...but I have gotten into the habit of swirling it around to mix it with bucket water before I pour into tank. I kinda like the idea of dosing the whole tank volume first though and then just pouring directly from tap....this would also assure you got all the chlorine out too.

Hmm...food for thought. Thanks for sharing!

[MickS77]

I use a Python to refill, I add dechlor once the water starts filling the tank. I've never noticed any issues.

[Liz hughes]

I do both depending on my mood as I’m running around doing all my tanks at once.  does it make a difference? I thought as long as I add it it’s ok 

[Brandy]

I don't pour straight to the tank--but that is not because I think that isn't a good idea, it is because I am cheap. I treat my replacement water in a 5g bucket, and I only add 5g worth of prime to the bucket. Then I start my water change (removal). By the time the temp on the bucket is right, and the tank is cleaned, I feel safe to add my fresh water without dosing the full volume of the tank. If I really think ahead, I draw the bucket the day before and don't use prime at all. If I ever get a python I will just use the direct to the tank full dose method.

[KBOzzie59]

99.9% of the time I add it as I'm filling to assist with mixing.

[Bill]

I fill a 5 gallon home depot bucket with water at desired temp and pump it into the the tank with a smartpond pump via tubing clamped into the tank. I adjust the flow so that its pumping at the same rate the faucet is filling it and treat it while its in the bucket. My faucets can't handle a python but this is the same thing and the pump and tubing were pretty cheap. 

This is the pump I use:

https://www.lowes.com/pd/smartpond-300-GPH-Submersible-Fountain-Pump/1000597013?cm_mmc=shp-_-c-_-prd-_-lwn-_-google-_-lia-_-243-_-pondsandfountains-_-1000597013-_-0&placeholder=null&gclid=Cj0KCQjw-uH6BRDQARIsAI3I-Ud6PqwovNolPPXp8BL5Y_tUEAsIeYXhHSTUYKwOSE_6t6WZuFuuoWYaAnmOEALw_wcB&gclsrc=aw.ds

Real easy as described here:

 

[ADMWNDSR83]

I have a 37g, and don't have a python or a tap that would work with a Python.  I add a few drops of dechlorinator (I have been using stress coat, but I'm getting ready to switch to Prime) to each bucket as it's filling.

[ADMWNDSR83]

3 minutes ago, Bill said:

I fill a 5 gallon home depot bucket with water at desired temp and pump it into the the tank with a smartpond pump via tubing clamped into the tank. I adjust the flow so that its pumping at the same rate the faucet is filling it and treat it while its in the bucket. My faucets can't handle a python but this is the same thing and the pump and tubing were pretty cheap. 

This is the pump I use:

https://www.lowes.com/pd/smartpond-300-GPH-Submersible-Fountain-Pump/1000597013?cm_mmc=shp-_-c-_-prd-_-lwn-_-google-_-lia-_-243-_-pondsandfountains-_-1000597013-_-0&placeholder=null&gclid=Cj0KCQjw-uH6BRDQARIsAI3I-Ud6PqwovNolPPXp8BL5Y_tUEAsIeYXhHSTUYKwOSE_6t6WZuFuuoWYaAnmOEALw_wcB&gclsrc=aw.ds

Real easy as described here:

 

I like the look of that, Bill!  I may have to hit Lowes tomorrow before my water change!

[jerseychef]

For three of my tanks I add the dechlorinator directly to the tank at the volume of the entire tank.  I do this just prior to turning the python on.  In my 4th tank that the python does not reach I simply fill up the home depot bucket with water and add the dechlorinator to it.  Since it is not going to be pushed around by the stream of the python I drop an airstone into the bucket to help move it around.  

[giantlumberjack]

I personally age my water after a water change. my water is used the second after i do a water change and the juges refilled so it as a week to age.

[Bill Smith]

When using tap water, I always always always treat my water before it goes in the tank. I see no reason to subject my fish even to a few seconds of chlorine/chloramine discomfort.

That said, I have had great success in recent months using a sediment filter/carbon block combination, even with chloramine hard water! I sprang for the 1 micron carbon block, and my water comes through chlorine-free and ammonia-free at all times. I hooked it up to the line that goes to my RO drinking water line, and I just open the valve when I need fish water.

 

[pedrofisk]

Before, unless of course I forget then after. Here in NYC our water is so good they barely put in chlorine in so I have very little risk. Sometime it is actually at zero. I used to premix in a garbage can to make sure them temp was right, it was declorinated and I added Equilibrium. Eventually I decided that effort wasn't worth it.

[Ben Ellison]

I use two five gallon jugs and treat about a minute before dumping typically about the time I have it all set up wait and it's filling the tank the other is full and I swap out. I'm always afraid of unseen damage to the gills. Maybe I'm a softy but I just can't bring myself to risk it 

 

Edited September 10, 2020 by Ben Ellison

[Sykes]

Reading through the replies here, I'm starting to think this is another case of everybody's thoughts are different because everybody's tap water is different. I've tested my unconditioned tap water and it has little to no chlorine to begin with (0.2 to 0.4 mg/L according to the local water quality report, but always reads 0 on my test strips), so I feel safe simply treating the tank. If my tests started showing higher chlorine levels (say above 0.5 mg/L), then taking the extra time to pretreat the tap water before adding to the tank would be more worthwhile.

[Streetwise]

I am mostly doing water top-offs to deal with evaporation. I verified with my water district that they do not use chloramine, so I just leave water out in buckets for 24-48 hours.

[ChefConfit]

My current town uses chloramine but at such a low concentration it doesn't show up on test strips so I add it straight to the tank and treat the whole tank with fritz complete. My old Town used chlorine also at an untestable level and I did the same thing. Also had no ill effects a couple times when I forgot to dechlorinate. If I had detectable levels in my tap water I would probably treat first but as it is I don't think there's much risk in exposing anything to chloramine that's already in undetectable amounts for a few seconds during a 20% water change. If I ever have to do a large 50%+ change I'd probably pre treat just to be safe. 

[Aquatic Journal]

I always add mine as soon as I am done filling up the tank and do not have any issues! The dechlorinator may not be instant but it won’t kill your fish instantly either. As long as you use the dechlorinator you should be fine!