# Very Sad Fish Massacre



## curiousburke (May 27, 2011)

Most of my adult fish died tonight. Ive always done big water changes every few weeks without a problem, but I did a large water change today that caused a massive fish die off. The dead are:
6 rosey barbs
2 SAE
3 cories
2 rainbows
5 giant danios 
2 adult Kribensis

The survivors so far are:
3 cories
5 rainbows
30 young kribensis
100 new kribensis fry
1 large gourami
7 otos

So, the survivors were the smallest fish in the tank except the gourami. The 2 cories and 2 rainbows were the last to go. The only thing that was a bit odd was that the water was very aerated. 

What do you think did it? Some thoughts: 
1) big water chemistry change, but why this time and not before? 
2) soap, would that be less lethal to small fish
3) temperature shock


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## Calmwaters (Sep 2, 2009)

So sorry for your loss. It could be either of the things you mentioned. What did they do before they died? Such as swim side ways, or stay at the top of the tank for example. How would you get soap in your tank? You should always have a bucket that is only used for water changes. Do you have city water or well water?


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## curiousburke (May 27, 2011)

they swam funny, some upside down or in circles. Some jumped out. Distressed for sure. In the end they all floated before they died. Actually, that's not true, some sank.

I fill with city water and treat in the tank with prime. I put the prime in before the water. I've been doing this for awhile though. I use a hose straight to my kitchen sink. The only way soap could get in is if my sink backed up while the dishwasher was running. I don't think this happened, but it is a possibility. In this case a little dish water could have got on the end of the hose. If it was soap would you expect that to spare the babies?


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## Calmwaters (Sep 2, 2009)

Sounds to me like they went into shock either due to a major swing in temp. or ph but I am leaning more towards temp. It maybe that the adult fish swam through the incomeing water while the babies and smaller fish stayed out of the way. It is very important when changeing water to keep the temp close to the same temp as whats in the tank.


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## curiousburke (May 27, 2011)

between pH and Temp, I would guess temp. I did correct the temp upward a couple degrees after they started swimming funny, but they just kept on dying.


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## Calmwaters (Sep 2, 2009)

Temp shock kills them pretty quickly.


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## curiousburke (May 27, 2011)

how many degrees would I have to be off? How could this explain that my largest fish and all my small fish survived.


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## Calmwaters (Sep 2, 2009)

Maybe the affected fish were closer to were the water was going in the tank not sure just a guess. The temp would not have to be off by much to put the fish in shock. It may not have been the temp but the way you described what they did makes me think it was the temp. Someone else may come along and have another idea or know why it affected some fish and not the others.


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## Byron (Mar 7, 2009)

This is difficult to pin down without some data. Leaving aside any toxic substance like soap getting in the water, the most likely explanatio is a considerable fluctuation in the water parameters: hardness, pH, temperature, ammonia/nitrite/nitrate, metals, chlorine... . Any one of these could be the issue.

Do you have any idea of the pH, nitrate and temp prior to the water change, and then after? A tank's biology can change considerably in two weeks, and especially if the fish load is higher rather than lower, feeding amounts, plants, etc. This might well lower pH and/or raise nitrates to the extent that the new water would be vastly different. This is one reason why water changes should be more frequent, weekly at minimum; it creates more stability.

As not all fish were affected according to what you describe, we can probably rule out chlorine as this would have poisoned all the fish quickly or equally. A significant change in pH or nitrates would affect different fish differently. Temp too.

Byron.


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## curiousburke (May 27, 2011)

Well, I know the pH before was about 7 and after was a little higher about 7.2 or 7.4. I find the scale difficult to read in that range. Its certainly a smaller pH change theh I has done in the past, so Im pretty sure it is not pH. 

I dont know the hardness. I do know that I add baking soda periodically to keep the pH up, so if that raises the hardness then there would have been a drop in hardness with the water change. I have been doing that more recently so the effect this time might have been bigger. I've never lost fish with a water change before.

I did not check the nitrates before, but knew they would be high, which is why I did a big water change. I am overstocked and it was a little longer than I usually go between water changes. They are between 20 and 40 now, so probably 100 to 150 before.

I have not lost more fish since last night, which is a relief. However, I don't know if I can save the kribensis fry. They are out of the cave now, which they never have been before, and just waiting around. I put another small tank upside-down over the area to protect them from the rainbows, but some have somehow escaped. I did feed them some baby brine shrimp, but I'm not sure if they can even eat them now. All the other batches had a very good mom to protect them through the early days.

hardness or water temperature makes the most sense to me. The water temperature before was 74 (that is the temp now, so it should have been the temp before since I have not changed the thermometer) and the temperature after was 72 maybe as low as 71. The swing couldn't have been more than 4 degrees.

Are gouramis really, really hardy fish? Whatever did it mostly killed large fish, except my gourami which was by far the largest fish in the tank.


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## Byron (Mar 7, 2009)

I do see some issues, though not saying these were the actual cause. But combined, may have contributed. I'll explain.

First, I would not use baking soda (sodium bicarbonate). Stanley Weitzman, who probably knows more about characins than anyone alive, has written that this is not a good substance for maintaining a pH balance. He says, sodium bicarbonate has no effective buffer action and cannot stabilize pH in the face of additional acidic waste products. And continual use will cause the sodium ions to reach intolerable levels for fish.

To the nitrates, any level above 20ppm is now believed to be detrimental to most tropical fish long term. Many have written that nitrates up to even 400ppm is not much of an issue, but the scientific data does not support this thinking. I would have to dig into my research to find the specific information, but this should make sense when one realizes that most of the fish we maintain in aquaria occur in water with nitrates so low they usually cannot even be measured. And excess nitrogen in any form, be it ammonia, nitrite, nitrate or nitrogen gas, is detrimental. Even ammonium which is basically harmless is rapidly assimilated by plants. But allowing nitrates to increase to the levels you mention is more than the plants can handle, if they are present.

I would not expect the rapid lowering of nitrates to cause fish deaths, but the elevated levels clearly, in my view, have weakened the fish so this may be one factor in the equation. The pH plays into this; at an acidic pH, ammonia changes to ammonium. But as soon as the pH rises above 7, the ammonium changes back to highly toxic ammonia, and this shock could easily kill some fish. As the pH readings are not absolute, this could be part of the problem. When an aquarium has gone without more significant water changes, it is much safer to change less water and do it more frequently in order to bring the biology back to safe levels.

Which brings me to the water changes. Weekly is the absolute minimum, especially in tanks that are overstocked as you mention. Fish are better able to tolerate gradual changes whether worsening or improving, but a sudden change either way may affect them significantly, even causing death. Not knowing what fish in what sized tank, I can't suggest adequate water changes but assuming there are no plants, half the tank every week is advisable once it is back in balance; getting there i would do more frequent changes with less volume, gradually building up. Even nitrates and pH cannot be used as a method of determining water changes, as some wrongly think. There is all the "crud" that is completely unmeasurable and cannot be removed by any amount of filtration. Only a water change removes this, and it is vital. Plants are the only natural "filters" for this, but that is only workable in very minimally-stocked and thickly planted tanks.

To the other parameters mentioned. Hardness would only change via the source water, unless you have something in the aquarium to affect it such as a calcareous substrate. This is where the water supply enters; if there is any chance that your local supplier might adjust the water chemistry, water changes must take this into account.

Temperature of a couple degrees would not of itself kill fish except perhaps for some highly sensitive species. Many of us do water changes and either deliberately or inadvertently lower the temperature by 3-4 degrees. A similar rise is also in itself not problematic.

Hope this helps in understanding things.

Byron.


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## curiousburke (May 27, 2011)

Reading your comments about substrate brought back one more component to my mind. This is the first time I have changed the tank water since I added new gravel. I recently took out all my old ea gravel and replaced it with CaribSea Instant Aquarium Peace River Gravel and I used the water conditioners they supplied. That has to be the problem (Id like it to be). There could have been all sorts of stuff in that gravel that I took out with a huge water change. 

As much as I want the truth, I would also like to think it wasnt just my stupidity in getting the water temp correct that killed them.


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## Byron (Mar 7, 2009)

There is no way a temperature difference of up to 4 degrees could have killed so many fish of the species named.

Changing the substrate is certainly another factor. A host of beneficial bacteria went out with the old gravel. Which meant that there would be fewer bacteria to handle any increase in ammonia.

The pre-death actions you initially described are common with poisoning by ammonia/nitrite/nitrate, and significant pH changes. I still believe it was likely a combination of things.


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## gupgram (Jun 11, 2011)

*String algae and Brazilian Pennywort*

Hmm, I have string alage that keeps growing JUST on portions of my Brazillian Pennywort. The roots turn very very dark green and there it will be, not bad but there. So I took out the portions that I could find the string algae but in little areas it is coming back. It has not grown on any other plants at all which seems starnge to me. I have lutea and flamming sword. The Pennywort I have thinned many times really grows. My concern is that the string algae will spread to the other plants. This has been going on for 2 months now. Wouldit be better to just get rid of the Pennywort? The other plants are beautiful and full so wouldn't be a great loss. Input would be appreciated please. Thank you!
Gupgram


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## curiousburke (May 27, 2011)

I have no measurable ammonia now. I think the high nitrates supports that the ammonia was probably zero yesterday.

I adjusted my pH the day before and my tap comes out at 7.6 so I know it wasnt a huge pH swing.

The particular substrate I used was meant not to be washed because it comes with bacteria, and it came in its own liquid. Does it make sense that that could have raised the hardness? If so, would the hardness have gone up slowly such that the fish survived the addition of the gravel? Now what should I do? How do I measure the hardness ... I guess there si a test?

thank you Byron and CalmWaters for your help with this. It came as such a shock since I didnt feel like I did anything all that different from what I have been doing. The nitrates were definitively higher than normal before this change.

edit: I just read on the CaribSea description that it doesnt change the hardness


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## Byron (Mar 7, 2009)

curiousburke said:


> I have no measurable ammonia now. I think the high nitrates supports that the ammonia was probably zero yesterday.
> 
> I adjusted my pH the day before and my tap comes out at 7.6 so I know it wasnt a huge pH swing.
> 
> ...


I've previously set out the individual issues that may have caused the problem individually or collectively. The main thing is to ensure it does not occur again. And the best way to do that is with regular partial water changes, meaning every week without fail. Nitrates cannot be allowed to rise above 20ppm. You will have to monitor things and if the parameters between tank water and tap water are reasonably close, a water change of 50% weekly will help. If there are significant differences you will have to adjust accordingly. If nitrates still are high with weekly changes, then either the fish load must be reduced or more frequent water changes are necessary. There are aquarists who do water changes every 3 days when it is needed.


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## curiousburke (May 27, 2011)

I agree, making sure it doesn't happen again is what is important, but I dont think I can really guarantee that without finding the cause.

another possibility that I came across is that the water outgasing could give the fish the bends. If this actually happens, then it sounds quite likely the cause to me. The water was much more gassy than normal; even my pum was getting gas in it. The problem is, doing more frequent water changes isn't going to eliminate this unless I let the water sit.

I'm biased against thinking the nitrates lowered the fish health because it was only a couple weeks and I have friends that go many weeks with nitrates through the roof with no apparent ill affects. Im not saying I dont believe it, but it seems unlikely to me.


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## Byron (Mar 7, 2009)

Excess gas/air in the tap water is another possible.

On the nitrates, I mentioned earlier that while this is not the likely issue it would likely weaken some fish, and anything that does that is part of a problem because it makes them more susceptible to other issues that otherwise might be fought off.

And I can say that I doubt you will find anyone on this site who does not recommend weekly partial water changes and keeping nitrates below 40ppm and preferably below 20ppm. The long-term effect of both of these cannot be understated. They are in my humble view the foundation of good aquarium management.


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## curiousburke (May 27, 2011)

Byron said:


> Excess gas/air in the tap water is another possible.


so, do I need to let the water sit? Or, would doing a 50% water change have reduced this effect sufficiently?



Byron said:


> And I can say that I doubt you will find anyone on this site who does not recommend weekly partial water changes and keeping nitrates below 40ppm and preferably below 20ppm. The long-term effect of both of these cannot be understated. They are in my humble view the foundation of good aquarium management.


I agree ... or at least I try to. I usually do 50% every 2 weeks.


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## curiousburke (May 27, 2011)

I'm becoming more convinced by the "Gas Bubble Disease" hypothesis. I didnt mention this before, but the fish also had bubbles on their fins. They often get these when I do a water change, but it was worse this time.

So, is there any other way to combat this than letting the water sit?


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## Byron (Mar 7, 2009)

On the air/gas in the tap water, I have seen this from time to time. I ignore it, and in 20 years have never been aware of any issues. I can't say if it may be trouble if severe. Perhaps other members who have more experience in this can comment.

Water changes* must* be weekly. There is considerable evidence now with respect to the benefits. We have had threads elsewhere on this forum about this, and I am not going to repeat. In your situation, it is even more critical. You admit your tank is overstocked, and nitrates at 100ppm prove it. I realize some people ignore their fish and have crowded small tanks and the fish somehow manage to survive with high nitrates. But that does not mean they are healthy. You can keep a dog in a 3x3 foot cage in the back yard and never let it out; it will live for many years probably, but is it healthy? I doubt it. I do 50% water changes on all my tanks every week, and have done for more than 15 years. This is just responsible husbandry; it's part of the requirement for maintaining healthy aquaria.


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## Calmwaters (Sep 2, 2009)

Very well put Byron.


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## curiousburke (May 27, 2011)

Byron, I'm not disagreeing with anything you are saying about tank maintenance, but I just don't see that it addresses the point of this thread, which is how my fish died. 

I'm feeling battered with this proper maintenance advice, when what I was hoping for was advice on how not to kill my whole tank again. If I was one of those tank owners that seldom changes the water then there are lots of reasons for the fish deaths, but that just isnt the case. Okay, I stretched this change out a couple more weeks than I usually do, but I dont see that doing it. If you could point me to any evidence that a drop in nitrates kills fish then I could see the link.


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## Byron (Mar 7, 2009)

curiousburke said:


> Byron, I'm not disagreeing with anything you are saying about tank maintenance, but I just don't see that it addresses the point of this thread, which is how my fish died.
> 
> I'm feeling battered with this proper maintenance advice, when what I was hoping for was advice on how not to kill my whole tank again. If I was one of those tank owners that seldom changes the water then there are lots of reasons for the fish deaths, but that just isnt the case. Okay, I stretched this change out a couple more weeks than I usually do, but I dont see that doing it. If you could point me to any evidence that a drop in nitrates kills fish then I could see the link.


I believe you are missing the crucial point in all this. Throughout I have said that several things could be responsible, and most likely collectively. From your description, there was obviously something in the water--and this could have been either a substance in the tap water, or a result of the tap/tank water mixing, or both--that affected the fish. No one of us is going to be able to put their finger on "the" issue, since we cannot take water tests, we wouldn't know what to test for, and most likely it was a combination of things.

We have no way of knowing if it it was something toxic in the tap water. I would assume not. A significant shift in pH in the tap water might have caused it; a significant level of ammonia or nitrite [one of our members experienced this, after a water change fish began dying and a test of the tap water indicated nitrite which had never been detected before]; an increase of chlorine or chloramine, though this would have been handled by the conditioner unless it was under-dosed [which I experienced once]. And the other external source possibility is something like soap, which was mentioned.

If the above was not the cause, then it had to be a reaction within the tank caused by the water change. I mentioned a pH shift and I am still leaning to this. If the tank was acidic, and given you subsequently said the substrate was recently replaced, which I noted would have killed a significant level of bacteria, the excess of ammonia caused by this would be ammonium [in acidic water] which is basically harmless. But as soon as the pH rose above 7 with the water change, all that ammonium changes back into ammonia. And the fish reaction you mentioned could be from ammonia, nitrite or a significant pH change. Chlorine also causes such reactions, though usually with excessive hanging at the surface.

To avoid this, weekly water changes are essential. That is most likely why this occurred. The high nitrates and probable lower pH is indicative of deteriorating water conditions. I believe this is directly answering your question:



> I'm feeling battered with this proper maintenance advice, when what I was hoping for was advice on how not to kill my whole tank again


I'm sorry if this isn't clear. It is my view as to what occurred, in the absence of any other possible cause. And the* only* way to avoid repetition is regular maintenance via water changes.

Byron.


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## curiousburke (May 27, 2011)

Byron said:


> I believe you are missing the crucial point in all this. Throughout I have said that several things could be responsible, and most likely collectively. From your description, there was obviously something in the water--and this could have been either a substance in the tap water, or a result of the tap/tank water mixing, or both--that affected the fish. No one of us is going to be able to put their finger on "the" issue, since we cannot take water tests, we wouldn't know what to test for, and most likely it was a combination of things.


I see this as a puzzle and with enough information (even without measurements) and reasoning someone could actually put their finger on it. For example, I did not mention the bubbles on the fishes fins at first, until I came across gas disease mentioned online.



Byron said:


> We have no way of knowing if it it was something toxic in the tap water. I would assume not. A significant shift in pH in the tap water might have caused it; a significant level of ammonia or nitrite [one of our members experienced this, after a water change fish began dying and a test of the tap water indicated nitrite which had never been detected before]; an increase of chlorine or chloramine, though this would have been handled by the conditioner unless it was under-dosed [which I experienced once]. And the other external source possibility is something like soap, which was mentioned.
> 
> If the above was not the cause, then it had to be a reaction within the tank caused by the water change. I mentioned a pH shift and I am still leaning to this. If the tank was acidic, and given you subsequently said the substrate was recently replaced, which I noted would have killed a significant level of bacteria, the excess of ammonia caused by this would be ammonium [in acidic water] which is basically harmless. But as soon as the pH rose above 7 with the water change, all that ammonium changes back into ammonia. And the fish reaction you mentioned could be from ammonia, nitrite or a significant pH change. Chlorine also causes such reactions, though usually with excessive hanging at the surface.


I know that nobody is going to say conclusively how this happened, but I was hoping someone would have experienced something similar. From my own experience, which is not long, but I have dealt with a number of problems, it just doesn't match pH or ammonia. Early on you helped me with mysome tank problems one of which was that my ammonia was through the roof, well I certainly diped into ph > 7 without having an instant fish die off or any for that matter. Ive also swung the pH more with baking soda then it would have swung this time without any fish death.

Excepting temp and pH changes, has anyone reading lost all or part of their populations of several species of fish within an hour or changing their water and do you know why? Does out-gassing behave like this, and has anyone here experienced it?



Byron said:


> I'm sorry if this isn't clear. It is my view as to what occurred, in the absence of any other possible cause. And the* only* way to avoid repetition is regular maintenance via water changes.
> Byron.


The problem is that regular maintenance will not avoid this happening again if regular maintenance is not the problem, that is why I keep looking for conclusive possible causes.

I thought of another piece of the puzzle, Gourami can breath air, so maybe she didnt suffer as much from the out-gasing because she resorted to air breathing. She is the only big fish I didnt loose.

another thing that strikes me is that if poor initial health was a factor, then I would think fish would continue to die after the event due to the shock of it, but it seems that the fish that survived the hour survived.


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## e2paradise (Nov 10, 2011)

ohhhhhhhhh so sorry to hear that, you need put coral reef and small fish inside tank, so the fish will not easy to die, don't always change water, it is not good for fish,


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