Why Did My Fish Die After Large Water Change?

[TropicalV]

2 nights ago, I did a 75% water change, properly vacuumed the gravel & rearranged some of my plants which caused the water to become murky from hidden dirt under the gravel. The following day, half of my fishes were dead and the remaining 3 neons seem to have fin rot overnight. I am fairly new to fish keeping, but I do my very best to keept he tank in tip top condition and feel very saddened and guilty for the deaths :'(

Tank information:
- 24 gallon tank has been set up for more then 3 months.
- Heavily planted, no rotting plants.
- 25-50% water changes twice a week since set up.
- Anti-chlorine always added in water before adding water into tank.
- 1 teaspoon of salt and 1 capful of beneficial bacteria added on each water change.
- 2 corys, 11 neons, 2 guppies, 2 white clouds, 4 rummy nose (8 neons & 4 rummy nose died and remaning 3 neons now have what seems to be fin rot)
- All fish get along very well, even schooling fish though they are not in numbers of 6 or above. No fin nipping, fighting, etc.
- Water: PH 7.4 (tap water is 7.2), Ammonia 0, Nitrite 0, Nitrate 5.0 (sometimes Nitrate is 0 a day after water change, is this normal?)

My questions:

What could have been the cause to the high number of deaths?
Can fin rot appear overnight? (half of the top and tail fins are gone, with white bits on the edges. Seems to be getting worse)
How can I treat fin rot without using chemical meds?

Thank you for your help...

 

[snazy]

2 nights ago, I did a 75% water change, properly vacuumed the gravel & rearranged some of my plants which caused the water to become murky from hidden dirt under the gravel. The following day, half of my fishes were dead and the remaining 3 neons seem to have fin rot overnight. I am fairly new to fish keeping, but I do my very best to keept he tank in tip top condition and feel very saddened and guilty for the deaths :'(

Tank information:
- 24 gallon tank has been set up for more then 3 months.
- Heavily planted, no rotting plants.
- 25-50% water changes twice a week since set up.
- Anti-chlorine always added in water before adding water into tank.
- 1 teaspoon of salt and 1 capful of beneficial bacteria added on each water change.
- 2 corys, 11 neons, 2 guppies, 2 white clouds, 4 rummy nose (8 neons & 4 rummy nose died and remaning 3 neons now have what seems to be fin rot)
- All fish get along very well, even schooling fish though they are not in numbers of 6 or above. No fin nipping, fighting, etc.
- Water: PH 7.4 (tap water is 7.2), Ammonia 0, Nitrite 0, Nitrate 5.0 (sometimes Nitrate is 0 a day after water change, is this normal?)

My questions:

What could have been the cause to the high number of deaths?
Can fin rot appear overnight? (half of the top and tail fins are gone, with white bits on the edges. Seems to be getting worse)
How can I treat fin rot without using chemical meds?

Thank you for your help...

Honestly, it is so typical for sudden ammonia rise to cause what seems like fin rot overnight, but you say this is 0 ?
I'd test the water again.
Are you using liquid tests? Nitrate can't be 0 really either in a normal cycled tank, though yours is heavily planted and the plants are eating a lot of it I guess. If you are using Api liquid test kit you need to shake the hell out of bottle 2 to get the right result for nitrate.
Maybe the large water change stressed them? Why did you do a 75% water change? Whatever was in the gravel, or the sudden change in water conditions stressed them. Did you make sure you matched the water temperature too?

On a side note I see that you are adding salt to the tank too. Some of these species like corys are salt intolerant and people say that for long periods of times it will kill them. And also, if you are adding the same ammount of salt on each water change you are causing the salt to build up too as the ammount of salt you need to add has to be proportinal to the water ammount changed, not the same dose. You don't need to add salt to your tank

I'd test the water again, and although it could have been the water change that stressed them, I'd do another water change in case you accidentally contaminated the tank somehow.

 

[PrairieSunflower]

Nothing to add but interested to see what happens. A couple of months back a similar thing happened in my tank... HUGE variety of symptoms including quick fin rot, also not caused by ammonia spiking. My entire tank of fish ending up dieing though... still not sure what happened and have been paranoid since!

Hope yours turns around though!

 

[TropicalV]

Honestly, it is so typical for sudden ammonia rise to cause what seems like fin rot overnight, but you say this is 0 ?
I'd test the water again.
Are you using liquid tests? Nitrate can't be 0 really either in a normal cycled tank, though yours is heavily planted and the plants are eating a lot of it I guess. If you are using Api liquid test kit you need to shake the hell out of bottle 2 to get the right result for nitrate.
Maybe the large water change stressed them? Why did you do a 75% water change? Whatever was in the gravel, or the sudden change in water conditions stressed them. Did you make sure you matched the water temperature too?

On a side note I see that you are adding salt to the tank too. Some of these species like corys are salt intolerant and people say that for long periods of times it will kill them. And also, if you are adding the same ammount of salt on each water change you are causing the salt to build up too as the ammount of salt you need to add has to be proportinal to the water ammount changed, not the same dose. You don't need to add salt to your tank

I'd test the water again, and although it could have been the water change that stressed them, I'd do another water change in case you accidentally contaminated the tank somehow.

Thank you so much for your reply and help

I've tested the water a few times using API liquid. The results today show 0 ammonia, 0 nitrites and 0.5 nitrates. I always do the tests exactly as the directions state, shaking each bottle accordingly.

I usually do a 25-50% water change, but that particular day, I vacuumed the gravel more then usual and the debris clouded the tank, so I changed more of the water to get rid of as much debris as possible. The temperature of the new water was matched to the tank water.

I have stopped using salt in my tank, goes to show that one should never listen tot heir local fish shops advice...

I have since purchased a small tank, which I have placed the sick fish in and treated them for finrot, so far they are doing well.

Could it have been the debris in the gravel that had killed the fish or maybe the gas buildup underneath the gravel from the plants?

 

[TropicalV]

Nothing to add but interested to see what happens. A couple of months back a similar thing happened in my tank... HUGE variety of symptoms including quick fin rot, also not caused by ammonia spiking. My entire tank of fish ending up dieing though... still not sure what happened and have been paranoid since!

Hope yours turns around though!

So sorry to hear that you too have experienced this, its heartbreaking to see so many fish die, I hope that there will be an answer to this mystery...

 

[snazy]

Could it have been the debris in the gravel that had killed the fish or maybe the gas buildup underneath the gravel from the plants?

It's quite possible but who knows. It could have been some type of toxic gas that was released. The debris itself won't do any harm unless it caused ammonia spike but since this is ruled out it must be something else. If you do 75% water change, make sure you add the new water slow enough for the fish to addapt to the new mineral content. I can't really think of anything else.

 

[Electric Warrior]

I don't know much about the other fish that you keep, except the S.A.'s, and neons and rummy nose definitely will not tolerate salt. Therefore, it is kind of interesting that they are the ones that did die right away.... Some say that rummy nose, and other tetras will be fine if you treat with a bit of aquarium salt in the instance of an ich outbreak, but I would not add any salt to a tank with tetras at all, unless you are treating and as a last resort. As for the possibility of toxic gas, I dunno... I have heard a lot of conflicting information about whether this could be true or not. I would tend to believe it's something else.

I have never had to deal with fin rot, but I hear that it can come on very quickly. IMO, I wouldn't ever do a 75% wc on a cycled tank, unless are you dealing with a toxin or emergency in your tank, like an ammonia spike, dropping a tub of food in, etc. You don't really need to. Your tank being planted should keep the nitrate down with just regular, smaller water changes. I do about a 30% wc, once a week, because I have fish that are pretty sensitive to water quality, and my nitrate usually falls from 10ppm before the change, to 5ppm after. I also check the water stats about an hour after a wc just to let things settle and get an accurate reading.

How long have you been adding salt to the tank? Like someone said above, water in the tank evaporates, but the salt content stays there, therefore adding salt after every water change could be like basically turning your tank marine after a while of doing this.

 

[TropicalV]

Could it have been the debris in the gravel that had killed the fish or maybe the gas buildup underneath the gravel from the plants?

It's quite possible but who knows. It could have been some type of toxic gas that was released. The debris itself won't do any harm unless it caused ammonia spike but since this is ruled out it must be something else. If you do 75% water change, make sure you add the new water slow enough for the fish to addapt to the new mineral content. I can't really think of anything else.

Thank you, I will surely do my best to make sure I wont stress my fish out ever again. I do trickle the water slowly so they dont go into shock. but now things are worse then they were before with an ICK outbreak... Im going to start a new thread to find out what I can do to save my fish... thank you again...

I don't know much about the other fish that you keep, except the S.A.'s, and neons and rummy nose definitely will not tolerate salt. Therefore, it is kind of interesting that they are the ones that did die right away.... Some say that rummy nose, and other tetras will be fine if you treat with a bit of aquarium salt in the instance of an ich outbreak, but I would not add any salt to a tank with tetras at all, unless you are treating and as a last resort. As for the possibility of toxic gas, I dunno... I have heard a lot of conflicting information about whether this could be true or not. I would tend to believe it's something else.

I have never had to deal with fin rot, but I hear that it can come on very quickly. IMO, I wouldn't ever do a 75% wc on a cycled tank, unless are you dealing with a toxin or emergency in your tank, like an ammonia spike, dropping a tub of food in, etc. You don't really need to. Your tank being planted should keep the nitrate down with just regular, smaller water changes. I do about a 30% wc, once a week, because I have fish that are pretty sensitive to water quality, and my nitrate usually falls from 10ppm before the change, to 5ppm after. I also check the water stats about an hour after a wc just to let things settle and get an accurate reading.

How long have you been adding salt to the tank? Like someone said above, water in the tank evaporates, but the salt content stays there, therefore adding salt after every water change could be like basically turning your tank marine after a while of doing this.

I had been adding salt for about 2 months, and now that I stopped adding the salt, I have a major ICK breakout, everything seems to be going wrong after that major water change... I feel completely helpless

 

[snazy]

Could it have been just a coincidence with the water change? Maybe the fish were already sick? Have added any new fish recently maybe? Hope they recover soon though.

 

[Flute]

Sorry to hear that you've been having so many problems

Just a thought, but could your water suppliers have put something in the water system? Apparently they do this every once in a while to clean things out. Might be worth contacting them to see if they had added any chemicals to the water systems on the day you did the big water change.