Water Change followed by Dead Fish

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The Masked Shadow

The Masked Shadow

Potamotrygon
MFK Member
Jul 19, 2020
4,968
5,361
164
Southern California (San Diego)
Have you tested your water?
Yes
If yes, what is your ammonia?
0
If yes, what is your nitrite?
0
If yes, what is your nitrate?
Less than 5
If I did not test my water...
  1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.
Do you do water changes?
Yes
What percentage of water do you change?
81-90%
How frequently do you change your water?
Every week
If I do not change my water...
  1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.
Tank size: 55g
Stock: 3 Congo Tetras (now 1), and 1 Delhezi Bichir (10 inches)

I am currently fighting a BBA algae breakout, and diatoms hell. At the time, it had been around a week and 3 days since I did a water change. I was gone for 5 days, and when I got back, I did a 90% water change. I scrubbed off all the diatoms and bba algae, and cleaned the gravel fully because the bba is growing on the sand. I follow every water change precaution, just like normal. Everything is great. I add water conditioner and everything. The water was quite cloudy, but nothing seemed out of the ordinary. So I watch the fish for 10 minutes once the water is in like usual, nothing is wrong. I’m gone for 2 hours. After, I come back and run upstairs to my fish. 2 of the Congo tetras are dead. One is acting all woozy. Im panicking, because I’m sure everything went right. I treat the tank with Aquarium Salt because maybe it’s because of the cloudiness of the sand or something. 10 minutes later, the fish is fine. Why did this happen? The Bichir wasn’t affected. I’ve had problems with Congo tetras, they seem to be very fragile fish when it comes to parameters. They are easily Stressed as well. There are no decorations, all are taken out for the algae. What could’ve happened? Did I do something wrong?
 
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Something must have gotten introduced.
Any bottles get knocked over, has the water company changed what goes in?
 
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Today just isn’t a good day for water changes ? in all seriousness, I’m sorry for the loss and if I had to guess then I’d say the water company changed their filtration and you didn’t know.
 
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IMO... u changed too much water/cleaned too much BB away... nothin kills fish quicker than crashing ur tank during a w/c... cloudy water after u fill up again is a sign of “re cycling”... some fish are “hardy” and can take it so many times, others will flop immediately... nothing stresses fish out more or quicker than a severe water change. This is why autodrip systems work so well, it removes all the stress from water changes. When u start keeping rare/tempermental fish u learn quickly the damages of water changes alone. Atleast its just a cple tetras lol... never clean ur filter and change water at the same time, same thing with scrubbin diatoms and gravel vac with a 90% change. 90% change regardless is unnecessary unless u have stored/aged/cycled water. We’ve all been there... u just did too much at once trying to “be clean” unintentionally making it worse...
 
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The Masked Shadow said:
Tank size: 55g
Stock: 3 Congo Tetras (now 1), and 1 Delhezi Bichir (10 inches)

I am currently fighting a BBA algae breakout, and diatoms hell. At the time, it had been around a week and 3 days since I did a water change. I was gone for 5 days, and when I got back, I did a 90% water change. I scrubbed off all the diatoms and bba algae, and cleaned the gravel fully because the bba is growing on the sand. I follow every water change precaution, just like normal. Everything is great. I add water conditioner and everything. The water was quite cloudy, but nothing seemed out of the ordinary. So I watch the fish for 10 minutes once the water is in like usual, nothing is wrong. I’m gone for 2 hours. After, I come back and run upstairs to my fish. 2 of the Congo tetras are dead. One is acting all woozy. Im panicking, because I’m sure everything went right. I treat the tank with Aquarium Salt because maybe it’s because of the cloudiness of the sand or something. 10 minutes later, the fish is fine. Why did this happen? The Bichir wasn’t affected. I’ve had problems with Congo tetras, they seem to be very fragile fish when it comes to parameters. They are easily Stressed as well. There are no decorations, all are taken out for the algae. What could’ve happened? Did I do something wrong?
Click to expand...
that's one of the reasons why I advocate against over 50 percent water changes, because large water changes remove the tank's buffer system so if something is wrong with the newly introduced water, then it will have a damaging effect on the water parameters.

Say I have a discus tank with pH of 6, and one day the local water pH changed from 6 to 8.
Well if you only do a 25 percent water change then your water pH is 6.5 if you do the math.
However if you do a 90 percent water change then your water pH becomes 7.8 which is large enough change to cause pH shock especially for fragile fish.

Thats why more frequent smaller WCs (like my cousin's 20% water change everyday) is better than a single large water change.

edit: btw a pH change of 1 is equivalent to a 10 times difference because pH is logarithmic so a pH change of 6.5 to 7.8 is a lot for a fish.
 
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SalviniCichlidFan said:
that's one of the reasons why I advocate against over 50 percent water changes, because large water changes remove the tank's buffer system so if something is wrong with the newly introduced water, then it will have a damaging effect on the water parameters.

Say I have a discus tank with pH of 6, and one day the local water pH changed from 6 to 8.
Well if you only do a 25 percent water change then your water pH is 6.5 if you do the math.
However if you do a 90 percent water change then your water pH becomes 7.8 which is large enough change to cause pH shock especially for fragile fish.

Thats why more frequent smaller WCs (like my cousin's 20% water change everyday) is better than a single large water change.

edit: btw a pH change of 1 is equivalent to a 10 times difference because pH is logarithmic so a pH change of 6.5 to 7.8 is a lot for a fish.
Click to expand...
But I’ve done 80-90% water changes before.
 
Absolutely nothing wrong with 90% water changes per se, and a lot that is good about them. But it is essential that you know what kind of water you are using. If I were using municipal water straight from the tap, I might not be willing to do that much...but then, depending upon what your local utility adds to the water, you could get disastrous results with a much smaller water change as well. Many years ago the city I lived in abruptly started using chloramine rather than chlorine, and there were many highly disgruntled local aquarists in the ensuing weeks and months. Just asking them to notify you of any changes isn't enough, since they often won't bother to do so. You need to test your water before using.

My well water is very stable, and I trust it to not change in any significant way from one week to the next. I will happily do a 90% change now that I have installed an on-demand water heater and a mixing valve that maintains a steady temperature throughout the change. Frankly, if I am going a water change at all, I just don't see the point in doing any less than at least 60 or 70%. Even fish and animals that are supposedly sensitive to major changes like that seem to do just fine; since I change a lot of water frequently, the tank water never has a chance to degrade too far, so the new water coming in is not that far different from the old stuff. But if you go weeks or months without a significant change, and then suddenly do a massive "fin-level" water change, you can experience bad results with sensitive animals.

In your case I think it's pretty clear that something was drastically different about the water you used; pH, temperature, and/or other parameters were far enough removed from the old water that the fish suffered shock. This isn't caused by doing a large water change; it's a result of using water that simply isn't suitable. Admittedly, the more you change, the greater the shock. But rather than just continuing to use lousy water and trying to compensate by only doing wimpy little water changes...find out what's wrong with the water, take steps to correct, and then change as much as you want. The more the merrier.
 
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Deadeye said:
Something must have gotten introduced.
Any bottles get knocked over, has the water company changed what goes in?
Click to expand...
No bottles fell over. I need to check the water companys Name and website
DrownedFishonFire said:
What water conditioner did you use?
Click to expand...
Prime Water Conditioner
wednesday13 said:
IMO... u changed too much water/cleaned too much BB away... nothin kills fish quicker than crashing ur tank during a w/c... cloudy water after u fill up again is a sign of “re cycling”... some fish are “hardy” and can take it so many times, others will flop immediately... nothing stresses fish out more or quicker than a severe water change. This is why autodrip systems work so well, it removes all the stress from water changes. When u start keeping rare/tempermental fish u learn quickly the damages of water changes alone. Atleast its just a cple tetras lol... never clean ur filter and change water at the same time, same thing with scrubbin diatoms and gravel vac with a 90% change. 90% change regardless is unnecessary unless u have stored/aged/cycled water. We’ve all been there... u just did too much at once trying to “be clean” unintentionally making it worse...
Click to expand...
So your saying my Tank isn’t cycled??? I only change one part of the filter once a month. Doesn’t the auto drop system take a while to fill up? The tank cloudiness was only during and 10 minutes after the water change. It’s probably the sand, because I meticulously vacuumed it.
jjohnwm said:
Absolutely nothing wrong with 90% water changes per se, and a lot that is good about them. But it is essential that you know what kind of water you are using. If I were using municipal water straight from the tap, I might not be willing to do that much...but then, depending upon what your local utility adds to the water, you could get disastrous results with a much smaller water change as well. Many years ago the city I lived in abruptly started using chloramine rather than chlorine, and there were many highly disgruntled local aquarists in the ensuing weeks and months. Just asking them to notify you of any changes isn't enough, since they often won't bother to do so. You need to test your water before using.

My well water is very stable, and I trust it to not change in any significant way from one week to the next. I will happily do a 90% change now that I have installed an on-demand water heater and a mixing valve that maintains a steady temperature throughout the change. Frankly, if I am going a water change at all, I just don't see the point in doing any less than at least 60 or 70%. Even fish and animals that are supposedly sensitive to major changes like that seem to do just fine; since I change a lot of water frequently, the tank water never has a chance to degrade too far, so the new water coming in is not that far different from the old stuff. But if you go weeks or months without a significant change, and then suddenly do a massive "fin-level" water change, you can experience bad results with sensitive animals.

In your case I think it's pretty clear that something was drastically different about the water you used; pH, temperature, and/or other parameters were far enough removed from the old water that the fish suffered shock. This isn't caused by doing a large water change; it's a result of using water that simply isn't suitable. Admittedly, the more you change, the greater the shock. But rather than just continuing to use lousy water and trying to compensate by only doing wimpy little water changes...find out what's wrong with the water, take steps to correct, and then change as much as you want. The more the merrier.
Click to expand...
IMO, this sounds accurate. I’m going to check the website. From now on, I’m checking the PH and whatnot before.
 
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