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Lost my pygmy corydoras after a water change

C

Calamardo Tentaculos

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4 Sep 2023
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London
Hi all,

I am just sharing that I lost a few of my pygmy corydoras after a rushed 50% water change. I did not heat up the water enough and an hour after the water change, all my pygmy corydoras were swimming erratically and two died within a day.

Absolutely galling to make such an amateur mistake. I plan to stick to smaller but more frequent water changes from now on.
 
Sorry to hear that. Heartbreaking.
I am Ken said:
I am just sharing that I lost a few of my pygmy corydoras after a rushed 50% water change. I did not heat up the water enough and an hour after the water change, all my pygmy corydoras were swimming erratically and two died within a day.
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Assume you treated the water for chlorine and chloramines?
Also, do you know how warm/cold your water was when this occurred? As @LightingBamboozled said, it should not be too much of an issue down to 22 or even 20 as a brief temperature excursion. Below that, I agree you could run into problems.
 
LightingBamboozled said:
I'd be surprised if cold water change was what did it for the cories. Pygmy cories like it down around 22 and the woman I knew who bred them did semi regular 25% water changes with 8C Fridge cold water to stimulate breeding.
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BRJP1 said:
Sorry to hear that. Heartbreaking.

Assume you treated the water for chlorine and chloramines?
Also, do you know how warm/cold your water was when this occurred? As @LightingBamboozled said, it should not be too much of an issue down to 22 or even 20 as a brief temperature excursion. Below that, I agree you could run into problems.
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Yes, I mix 50:50 RO and tapwater, treating it with Seachem Prime.

Honestly, the water change is the only thing I can trace it to as they started swimming erratically an hour after the water change, eventually falling to the bottom upside down. After a day or two, they died.

I am honestly wondering what am I doing wrong.
 
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Well, that is an odd one to diagnose. Assume the others have survived and settled down now?
The only thing I can think of is to test the TDS of the water you mixed to ensure there was enough in there. Obviously, RO water has no/low minerals and needs to be re-mineralised, but you mixed it with tap water.
I did a 50-litre water change (50%) last week with tap water, dechlroninator and temperature matching, and nothing happened.

Would you be able to send a picture of your tank and the remaining fish?
 
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Are any other fish in the aquarium? Its ?a pure guess but ammonia would be suspect for what you describe IMO. Is it your own RO or from a shop?
 
Also, could you send your Ammonia and Nitrite levels just for good order's sake?
PARAGUAY said:
Are any other fish in the aquarium? Its ?a pure guess but ammonia would be suspect for what you describe IMO.
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That would have to be some high Ammonia in the water introduced by the change. I wonder if it is more mineral issues or chlorine-related? Certainly an odd one.
 
I have pygmy Cory too, initially the tank was tap water only, but In the last 3 weeks I'm switching to 100% ro.

About temp, the tank is at 22°, while the water change that I do (50%) is usually around 18-19 (140 litres wc, the tank is 330L) so around 1-2° swing. My pygmy, during WC, swim exactly where the colder water is dropping. They are "affected" both to a temp "change" and tds too (usually the tank sits at 260-280ppm tds while the WC water is around 140 tds. They are very active after the WC.
 
riioKen said:
I have pygmy Cory too, initially the tank was tap water only, but In the last 3 weeks I'm switching to 100% ro.

About temp, the tank is at 22°, while the water change that I do (50%) is usually around 18-19 (140 litres wc, the tank is 330L) so around 1-2° swing. My pygmy, during WC, swim exactly where the colder water is dropping. They are "affected" both to a temp "change" and tds too (usually the tank sits at 260-280ppm tds while the WC water is around 140 tds. They are very active after the WC.
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Yes, this would all make sense. Fish are more resilient to water temperature changes than people think - 1-2 degrees usually does not cause much of a problem at all.
 
Below is a picture of my tank.
IMG_20231213_231733.jpg
 
BRJP1 said:
Also, could you send your Ammonia and Nitrite levels just for good order's sake?

That would have to be some high Ammonia in the water introduced by the change. I wonder if it is more mineral issues or chlorine-related? Certainly an odd one.
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The guppy and amanos are unaffected. I would have thought that the amanos would be the first to suffer any ammonia reaction.
 
If it’s the first time you’ve done such a waterchange without heating the water, then I’d suspect you’re correct on it being the cause.
There are temp swings, and then there are temp swings. If the water was really cold, then it would obviously cause enough of a swing to shock the fish.
 
Sorry for your loss, I can imagine you are kicking yourself.

How cold was it? As others above, I regularly drop mine during a water change/top up. Mine go from 24oC to about 21/22. The heaters a bit oversize so heats it back up pretty quick. It's one of the things that seems to trigger breeding the next day and they never show any distress at the time.

Just because they tolerate this though, doesn't mean that any temp change would be okay. I have been more careful lately though as the rain water I top up with is outside so at it's coldest at the moment. I've been bringing a bucket to sit inside to warm up a bit (about 18oC) before topping up or topping up more gradually (I usually let it drop and then do 6l ish up in one go - the tank is 70l).

A thermometre with an alert might give you some piece of mind. My heater is on a temp controller, which has an audible alarm when the tank drops too low (or too high). I actually triggered it today when topping up (cold rain water) and it meant I stopped and left it to warm up before adding more.
 
www.ukaps.org

Hydrogen Sulphide

Hi everyone, First time posting on here as I’ve recently just joined! A little bit about me I have been in the aquarium hobby for almost 3 years now, but have recently started cultivating a planted aquarium. I have recently encountered the dreaded problem of hydrogen sulphide build up...
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your substrate doesn't seem deep enough for this problem, but just in case....
 
@I am Ken - I think there are some good plausible causes here, but it's hard to nail at the moment. As others have mentioned, a 50% water change should not be a problem if all parameters are correct during that change.

As we can't isolate the problem for sure, I can only suggest stepping back and doing some checks at this stage.
  • Test the water for basics to understand where you are right now (Ammonia, Nitrite, Nitrate, Chlorine, TDS, Temp ) and record that somewhere.
    • I would also test both your raw tap water and RO water for Ammonia, Nitrite, Nitrate, Chlorine and TDS to understand the readings at the source.
  • It looks like you have a sponge filter and assume that is working? Keep that running, and only clean it when it's clogged to let any bacteria build up. (i.e. let's not remove any goodness by over-cleaning).
    • I can't tell if it's the camera image due to light, but there is a certain amount of milky haze in the water - is that the camera light or is it crystal clear in reality?
  • Check/increase the aeration by upping surface agitation or enough air bubbles to create that agitation.
  • Stick your finger (gently to not disturb too much but enough to 'coat' your finger) into the gravel and give it a sniff test to check that it does not smell eggy or sewage-like.
I know none of this is an answer, and it could be a temperature issue caused by the change, but I would just take stock of the environment right now and check if anything comes to light.
 
I am Ken said:
Honestly, the water change is the only thing I can trace it to as they started swimming erratically an hour after the water change, eventually falling to the bottom upside down. After a day or two, they died.

I am honestly wondering what am I doing wrong.
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That doesn't sound like cold shock to me, the prime symptom I've seen in cold shock is lethargy. My instinct would be either toxin in the added water or toxin in the tank water made more toxic by the water change.

BRJP1 has given the exact advice I would. Test everything to see if there's a hidden problem.
 
I am Ken said:
I am just sharing that I lost a few of my pygmy corydoras after a rushed 50% water change
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If it helps I suspect the cooler 50% water change and subsequent fish loss are unrelated in the grand scheme of things. So don't beat yourself up about it.

Looking back at some of your other posts it appears you've already lost a number of pygmy corydoras over the last month or so, certainly before this water change?

Not saying this to be a smart ars#, but suspect either the tank or fish themselves have some underlying issue that's causing the loss, although admittedly I don't know what this could be.
 
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I am Ken said:
Hi all,

I am just sharing that I lost a few of my pygmy corydoras after a rushed 50% water change. I did not heat up the water enough and an hour after the water change, all my pygmy corydoras were swimming erratically and two died within a day.

Absolutely galling to make such an amateur mistake. I plan to stick to smaller but more frequent water changes from now on.
Click to expand...
Could be Oxygen depletion.
How much water did you change?
What time of day did you do it?
How much Seachem Prime did you dose into the RO/Tapwater?
 
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