# Danios dying after water change?



## vermiform

I have a 29 gal. community tank with two guppies, two dalmation mollies, and formerly three golden danios. It's been running quite smoothly since February, no fish deaths and no illnesses either.

Today, however, I performed a routine weekly 20% water change, and about five minutes later one of the danios was swimming weakly on his back with the guppies picking at him. I took him out and put him in a small bowl and he died pretty quickly. About ten minutes after this, a second danio started sitting lethargically at the bottom, and within another ten minutes he too was swimming upside down and died within minutes of being isolated. So far the third seems fine, no particular change in behavior. The guppies and mollies are all perfectly fine.

It was the first water change that I've done since introducing the danios to the tank about a week ago. I changed the same amount that I've been changing for the entire life of the tank. The temperatures of the tank and of the new water were each 75 F. The one thing I suspect might be the cause is pH. The pH of my tank has a tendency to buffer itself to somewhere around 7.8. I try to keep it down (theoretically 7.0, although it usually doesn't reach that) by adjusting the new water to 7.0 when I do changes. So far, this hasn't seemed to cause any harm to any of the fish except now possibly the danios.

What went wrong? Should I be worried about the third danio or the other fish?


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## Danh

The fish were fairly new... So who knows. Do you have something in the tank that's buffering the water? I don't do anything for ph with any of my tanks. I believe the possibility of fluctuation is much worse than trying match.


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## emc7

Mollies and danios don't mind high pH, so stop trying to change it. If you use pH down your fish might possibly have got a drop of acid. Much more likely is that adding new fish caused a "mini-cycle" and your ammonia or nitrite levels are temporarily up. pH affects the toxicity of ammonia, so the water change could have made things worse (before making them better by lowing the toxin levels). Or it was just one stress too many. Test your water if you can but don't stop the water changes.


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## Danh

I would lean more toward them being bad fish. I've never owned a danio that was easy to kill.. I haven't owned that many in the first place though. I had a long finned danio that lived in a canister filter for a few months.. All of your other fish looked ok, right?


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## Guest

danipo in a canister filter WHAT???????????


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## Danh

Yeah.. Somehow it got in there and I didn't realize it until I cleaned it. I thought my turtle had managed to eat it.


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## Justinslilbug

emc7 said:


> Mollies and danios don't mind high pH, so stop trying to change it. If you use pH down your fish might possibly have got a drop of acid. Much more likely is that adding new fish caused a "mini-cycle" and your ammonia or nitrite levels are temporarily up. pH affects the toxicity of ammonia, so the water change could have made things worse (before making them better by lowing the toxin levels). Or it was just one stress too many. Test your water if you can but don't stop the water changes.





 so are you saying that if you have mollys and danio's to not mess with the ph? all my guppies died(except the one pregnant one she is in a different tank)i also have a loach, and i cant keep the ph at a good level. so is it ok to do a water change and not worry about the ph levels?


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## Julie's Julies

Yes: please, please do NOT adjust pH levels. My pH is about 8.2 and I don't do anything to it. Adding pH down is just a temporary change anyway; there is a good chance that it will rebound shortly (in even just an hour) and this stresses fish out WAY more than just having a constantly high pH.

Instead, whenever you get a new fish, add 1/4 cup of tank water to the fish bag every half hour until you have more tank water than bag water. Remove the fish from the bag and place in your tank. Toss out all bag/tank mix water to avoid contamination. This is a very easy, low stress way of acclimating the new fish. I also do a pH check on the bag water; the greater the difference between the bag water and my tank water, the longer I take to acclimate my new little guy. You can also pop in an air stone since he'll be in the bag a while.


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## Obsidian

Yup, I have naturally fairly high PH (8.0) even with driftwood in the tank it just won't go down from there. Since it's not screaming high I just don't worry about it and figure they will be better off if they can get used to that level. I also take my time in acclimating, usually taking an hour to do this.


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## emc7

Guppies prefer hard, alkaline water. Unless you have specific fish that need soft water such as neons and discus, *leave you pH alone*. Changing pH causes stress to any fish. To do it regularly is just cruel. And it really easy to mess up and overdose with pH adjusting chemicals, thus killing all your fish. 

Adjusting the pH of the water change water is only necessary for the big water changes like betta keepers use, and it that case, *You adjust the water to match your tank*, not change it. pH changes in a tank should be done gradually, with great care, by a good buffer (such as Neutral regulator). 

I'll say it again, *don't use pH up and down*. I don't know why so many aquarium kits come with this stuff. You wouldn't pour caustic soda in your swimming pool, why inflict it on your fish?


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## mousey

I can't remember if it is this forum or the other that I frequent but there has been recent conversation about danios dying rather suddenly. So I am assuming it is the next problem in the tropical fish industry.--last year it was gourami issues and a few years ago it was angel fish problems.
My local Big Al's has had a lot of problems with danios just lately.


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## kamanut

I had some danios that did that also (died suddenly after a water change), while the other fish were perfectly fine. I have come to two possibilities of the deaths: 1) Since I used these fish for cycling, their immune systems were previously compromised, hence making them weaker and not able to adjust to a water change (any minimal change in temp, pH, chlorine, nitrate/nitrites, etc.) like the other fish or 2) There was something in the chlorine remover that triggered something in the danios that didn't trigger in the other fish. 

It was very weird and peculiar---they died almost instantly....and the other fish just swam around like usual. And it was always danios.....interesting.....


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## cat

I know this is an old topic, but it came up when I searched for 'danios water change'. I've lost 3 danios at different times due to water changes. The other fish were fine. Even other danios were fine. I did use a chemical to get the chlorine out of the water. I changed the water slowly to avoid a large temperature change. Has anyone found out why this happens?

The most telling thing for me is that one died within an hour of a water change and another acted sick staying at the surface. My other 3 were fine and the sick one recovered. At the next water change the one that had gotten sick at the previous change died, but the other three remained fine. That seems to eliminate a random bit of a chemical accidentally hitting that individual fish unless it was an incredibly unlucky little critter.


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## Plecostomus

When was the last time you did a water change? I've noticed that if you don't do a water change for a while, the ammonia and stuff can build up without seeming to affect the fish, but then if you do one big water change, the sudden change may shock or possibly kill fish.


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## cat

I change the water weekly. I have a pair of dwarf cichlids that need a 50% change weekly. When I lost the first of my danios I was doing 20% changes weekly.


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