Fish dead after water change

[Callisto405]

I have a 29 gallon tank that has been cycled for 2 months and have had no problems. I have been doing 25% water changes every week for the last 2 months since I added fish and have had no problems. Today I decided to do a 50% change due to high nitrates. The water temperature was exactly matched, I added tetra dechlorinator to the recommended amount plus a bit extra. Added a little API leaf zone for the plants. A little tetra water conditioner. Ph was 7.4 before the change and is 7.4 after the change.
1 zebra died immediately following the change (only one in tank)
4 of my 10 Mollys are swimming at the surface. The Dalmatian looks really stressed and a couple have a clamped dorsal fin
All my 5 Corey's(2 adult 3 small) are not active at all and are just lying there not moving. Sometimes some lay on their side and look like their dead. But when I touch them they swim again
Also there is 2 snails, a pleco ( moving to my 55 gallon) and 2 swordtails and 4 babies in the tank
I'm baffled, can someone tell me what's going on

 

[kwi]

When in the process did you add the dechlorinator?
What is in the water conditioner, does it also dechlorinate the water?
And what do your tests tell you now? (Ammonia, Nitrite, Nitrates)

 

[Callisto405]

Added 2/3 in first 5 gallon bucket. A sprits in the 2 bucket and the last 1/3 in the last 5 gallon bucket. Added water immediately after

 

[Callisto405]

When in the process did you add the dechlorinator?
What is in the water conditioner, does it also dechlorinate the water?
And what do your tests tell you now? (Ammonia, Nitrite, Nitrates)

Ammonia 0 nitrites 0 and nitrates 80 before change. Changed 50% of the water, didn't vaccume. It's a well cycled tank

 

[kwi]

And are you able to do a water test now?


And are you 100% certain that no hand sanatiser could of gotten into the tank, there is an ingredient in some that is highly toxic to fish.

 

[Callisto405]

And are you able to do a water test now?


And are you 100% certain that no hand sanatiser could of gotten into the tank, there is an ingredient in some that is highly toxic to fish.

Took a shower this morning. No work today so no hand sanitizer used. Washed my whole arm in hot water before putting it into the tank as I always do that

 

[Phreaker]

Check your tap water, does it maybe have a strong chlorine smell? They water company may have added more chlorine to the water than your dechlorinator could have handled.

 

[Callisto405]

Took a shower this morning. No work today so no hand sanitizer used. Washed my whole arm in hot water before putting it into the tank as I always do that

And are you able to do a water test now?


And are you 100% certain that no hand sanatiser could of gotten into the tank, there is an ingredient in some that is highly toxic to fish.

Ammonia between.25 ppm and .50ppm. nitrite 0.

 

[Callisto405]

Ammonia between.25 ppm and .50ppm. nitrite 0.

My tap water seems to have a bit of ammonia. But the fish for the most part are back to their active selves. Most the Corry are sifting again and the Molly's are swimming around again

 

[Callisto405]

My tap water seems to have a bit of ammonia. But the fish for the most part are back to their active selves. Most the Corry are sifting again and the Molly's are swimming around again

but something clearly went wrong as the zebra instantly died

 

[Colin_T]

You poisoned your fish. There was either chlorine/ chloramine in the tap water that was added to the tank, or something in the bucket you used. If there is ammonia in your tap water, you have chloramine in your water supply.

Do you have buckets specifically for the fish tank or do you use any bucket from around the house?

You need to dechloinate the new water before it goes into the tank. If the bucket holds 10 litres of water, you add enough dechlorinator to treat that 10 litres, aerate it for a couple of minutes so the dechlorinator can mix with the water and neutralise all the chlorine, then add that bucket of water to the tank. Do the same for the next bucket and so on.

If you just add a full dose of dechlorinator to one bucket but no other buckets of water, there will be chlorine/ chloramine going into the tank and poisoning will occur.

----------------------
Right now, add a double dose of dechlorinator to the tank. Add enough to treat the entire tank 2 times.

Increase aeration/ surface turbulence.

Add some carbon to the filter. Remove the carbon after a week.

 

[Callisto405]

You poisoned your fish. There was either chlorine/ chloramine in the tap water that was added to the tank, or something in the bucket you used. If there is ammonia in your tap water, you have chloramine in your water supply.

Do you have buckets specifically for the fish tank or do you use any bucket from around the house?

You need to dechloinate the new water before it goes into the tank. If the bucket holds 10 litres of water, you add enough dechlorinator to treat that 10 litres, aerate it for a couple of minutes so the dechlorinator can mix with the water and neutralise all the chlorine, then add that bucket of water to the tank. Do the same for the next bucket and so on.

If you just add a full dose of dechlorinator to one bucket but no other buckets of water, there will be chlorine/ chloramine going into the tank and poisoning will occur.

----------------------
Right now, add a double dose of dechlorinator to the tank. Add enough to treat the entire tank 2 times.

Increase aeration/ surface turbulence.

Add some carbon to the filter. Remove the carbon after a week.

I have had tanks for years. I use the same clean bucket I always use to change water. I always thourghly wash the bucket out with scalding hot faucet water. I use the bucket for nothing else. I added the water treatment before the water was added. 2/3 in the first bucket. The only thing I did do wrong is not add a full dose to the second bucket but I did add some to that bucket. Then 1/3 total dose in the last bucket. The total dose was more than called for.

From what I have read, chlorine kills fish over a short period of time, not instantly. If some of the chlorine wasn't instantly neutralized it wasn't much. It would not have killed the zebra within 2 mins of me finishing the water change.

What I will do in the future is add the proper dose to each bucket plus a bit extra, stir it and let it sit 15 mins before adding it. And instead of doing a weekly 50% change all at once I'll do a 25% change twice a week

 

[Utar]

I agree with everyone here somehow you accidentally poisoned your fish. But sounds like you where taking all the precautions to wash and clean your hands and arms, so it wasn't from your person, it had to be something different with your water source.What I think you should start doing is allowing the tap water to set in containers before using it for water changes, I use to use 2 1/2 gallon water containers the ones with spouts on them. Chlorinate the water and let it set for a week between water changes. Go back to doing small water changes and really clean your substrate to help with nitrates. Slowly with each water change increase the amount of water you change, allowing your fish to adjust to the changes in water.

 

[mcordelia]

This may be a n00b question, but how high do nitrates need to be for the situation to be considered "old tank syndrome"? When I was reading OP's original question my inner monologue was "oh no nitrates were really high and then got halved, that must have shocked the fish", but it doesn't sound like anyone else was thinking along those lines, so I'm just Monday morning quarterbacking this to try and figure out how you guys concluded "other source of poisoning"?
@Colin_T @kwi @Utar

 

[CassCats]

Your nitrates are 80ppm this is well over the safe zone. I would say that this has probably affected your fish at this level.

Also gonna point out, I add dechlorinator directly to my tank before I fill it with fresh water with a hose, so water is flowing into the tank for up to 10-15 minutes after dechlorinator is added. I have a lot of doubts about it being a chlorine issue.


OP, slowly change the water daily, a small bit, until your nitrates are below 20, better under 10. If they reach 20, do a water change in the future, 80ppm is high and a sudden change will shock fish, as mentioned above.