Water Change Wiped Out My Guppies

[Augustjd27]

Hey guys. I did a 25% water change on my 20 high fancy guppy tank and within 3 hours 4/5 adults and all 3 juveniles were dead. I'm not sure what the issue was and now I'm pretty afraid of ever doing water changes. They just seemed to drop dead with no major symptoms.

The water temp dropped by about 2 degrees but I figure that's too small to matter. I tested and the tank and tap pH are identical. Only possibility I see is chlorine or chloramine as I don't use dechlorinator, but I've never encountered this issue before.

 

Please feel free to share your thoughts on why they may have died. Thank you!

[lefty o]

2 degrees didnt do it, i would lean towards chlorine without any testing to prove things one way or the other. chlorine, or ammonia you will most likely notice their gills get extra red.

[Tony s]

It is possibly chlorine contamination. If you’re using a municipal water supply, most of those use a chlorine based water cleanser to prevent microbial buildup in the water supply. It’s not an instant kill either. Takes about an hour and a half to kill microbes. Probably longer for fish. So, if your on city water, a conditioner is a must.

If you’re on well water (I am), could be a metal contaminant. For me, it would be too much iron. I’ve had to go to RO water for the fish. My temperature fluctuates are usually more than 5 degrees and I’ve had no problems. I could fix that by adding a heater to a stock tank, but haven’t needed to yet 

Edited January 15 by Tony s

[Tlindsey]

On 1/14/2024 at 8:58 PM, Augustjd27 said:

Hey guys. I did a 25% water change on my 20 high fancy guppy tank and within 3 hours 4/5 adults and all 3 juveniles were dead. I'm not sure what the issue was and now I'm pretty afraid of ever doing water changes. They just seemed to drop dead with no major symptoms.

The water temp dropped by about 2 degrees but I figure that's too small to matter. I tested and the tank and tap pH are identical. Only possibility I see is chlorine or chloramine as I don't use dechlorinator, but I've never encountered this issue before.

 

Please feel free to share your thoughts on why they may have died. Thank you!

@Augustjd27 I believe your water parameters aren't stable. Dechlorinator prevents beneficial bacteria from being killed by chlorine, or chloramine depending on declorinator used. Without dechlorinater your aquarium isn't going to cycle properly. It's a possibility ammonia was present or critical difference of the PH at the time you did your water change.

Edited January 15 by Tlindsey

[mynameisnobody]

I’d bet the lack of dechlorinator was the root cause. 

[nabokovfan87]

I would think there was either some sort of contamination or dechlorination wasn't used.  😞

There was a youtube video that matches exactly what you experienced and the guy realized after he forgot dechlorinator.  I can't find the video because of search algorithm recommendation issues, but yeah....  I would recommend using dechlorinator.

My condolences.

[gabdewulf]

The more freezing the weather gets, the higher chlorines will be dropped in the supply.

[Galabar]

Going forward, use a dechlorinator like Prime.  There are a number of bad things that can happen with chlorine from untreated tap water.

Note that you have some leeway when adding the dechlorinator, as bacteria is killed over a somewhat "long" period of time when coming in contact with chlorine.

Edited January 15 by Galabar

[Seisage]

Echoing everyone else here in saying it was probably chlorine in the water, but I will add this:

You mention you've never run into this issue before. Well, you've probably just been getting lucky with the chlorine levels present in the tap being low enough to not cause harm. Some municipal water systems are being required to increase their chlorine concentrations to improve drinking water safety. Other systems will do occasional temporary "flushes" of chlorine for a variety of reasons. It sounds to me that for some reason, the chlorine concentration increased sometime between your last water change and this most recent one.

I'm sorry for your loss, and let this be a good lesson for the future.

[Chick-In-Of-TheSea]

First, I am so sorry for your losses. As others have suggested, my gut tells me chlorine. You can’t predict what the water companies will do to the water. One day the water supply may have no chlorine, and the next day chlorine and/or chloramines may be present. Most dechlorinators will remove heavy metals as well for the safety of the fish. As @Galabar and @Tlindsey have mentioned, chlorine will kill your beneficial bacteria as well and can lead to “new tank syndrome” (unstable parameters ie: ammonia spikes).

Edited January 15 by Chick-In-Of-TheSea

[TOtrees]

@Augustjd27 is there a reason you've avoided or not used decholor up to this point? I'm trying to ask this honestly and fairly, and without my own opinions on the matter being obvious... having difficulty 😞 Is it cost? Have you been told it's not necessary? Do you not trust the products or mfrs?

Was 25% a higher amount of water change than usual? Anything else different? New fish in the past few months? Plants? 

[Lonkley]

Not to pile on, but literally a few drops of dechlorinator would take care of it.

Now, you have a tank that has likely crashed it's cycle.  I would add dechlorinator now, and something like fritz 7 and try and get that cycle going for the survivors. Including cutting back on food since it'll be easy for that ammonia to build up.

Another possibility is you inadvertently added something to the tank from your skin.  Any oils, soap or the like?

Edited January 15 by Lonkley

[NOLANANO]

On 1/14/2024 at 7:58 PM, Augustjd27 said:

Hey guys. I did a 25% water change on my 20 high fancy guppy tank and within 3 hours 4/5 adults and all 3 juveniles were dead. I'm not sure what the issue was and now I'm pretty afraid of ever doing water changes. They just seemed to drop dead with no major symptoms.

The water temp dropped by about 2 degrees but I figure that's too small to matter. I tested and the tank and tap pH are identical. Only possibility I see is chlorine or chloramine as I don't use dechlorinator, but I've never encountered this issue before.

 

Please feel free to share your thoughts on why they may have died. Thank you!

Municipal water supplies can use more or less chlorine or other additives depending on the time of year and quality of water. I had an issue for a while where I would do a water change and all my fish would swim to the surface and breath heavily within an hour despite me using a dechlorinator.  The solution was to get an airstone and make sure there was plenty of gas exchange happening because there was something in the tap water that was suffocating the fish. The airstone allowed the "poison" to be extracted from the water quick enough to avoid harming my fish.

This was not an issue for me for the first 2 years of having an aquarium and it seems to have subsided but now I always keep an airstone going and I double dose Prime every time I do a water change. The point being that just because your tap water was fine prior, it can change and you'll have to adapt your process.

Edited January 15 by NOLANANO

[Augustjd27]

On 1/15/2024 at 7:48 AM, TOtrees said:

@Augustjd27 is there a reason you've avoided or not used decholor up to this point? I'm trying to ask this honestly and fairly, and without my own opinions on the matter being obvious... having difficulty 😞 Is it cost? Have you been told it's not necessary? Do you not trust the products or mfrs?

Was 25% a higher amount of water change than usual? Anything else different? New fish in the past few months? Plants? 

I know some fellow hobbyists who deliberately don't use dechlorinator as dechlorinator removes oxygen and chlorine may have some antibacterial benefits for the health of the fish. This was a pretty standard water change for me, but I think from now on I'll use dechlorinator just to be safe. Thanks!