Water-change killed my fish??

Hi everyone,

This actually happened a few months ago, but I need to resolve this issue before I purchase and new fish.

My 75-gal planted aquarium was thriving with 3 kuhli loaches, 8 corydoras, 10 rummy-nose tetras, 2 apisstogrammas, and 2 bamboo shrimp. About a week after adding the most recent batch of fish I did a 50% water change. A few hours later, nearly all the fish had died.

Now, I know that they were doing well prior to the water change. I tested the water and the rummy-nose were fully colored up. After pulling out all of the dead fish, I tested the water again and saw that nothing had changed with the water chemistry or temperature. Only the appistogramma pair and bamboo shrimp survived.

Key information:
I tested nitrite, nitrate, pH, chlorine, and temperature. Nitrate approximately 0, nitrite 0, and chlorine 0. Temp and pH remained the same at around 82 degrees and 6.2 pH.

The cause of their death must have had to do with the water change and cleaning. Upon draining the tank I moved some plants around sending some debris into the water column. I am not worried about a build up of methane or toxic gases being released since the planted section is lava rock. Then I filled it up the same way I always do with a hose attaching the sink to the aquarium. This is where things might have been risky; I always get the sink to close to the correct temp then fill up the tank, slowly dechlorinating the tank as the water level rises. I know it is risky to add tap water straight into an aquarium but my tap seems to be safe and I have changed the water like this many times.

Any ideas for how these fish died? Sorry for the long post, feel free to ask for any other information. Does anyone see an obvious flaw with my water change system?

Thanks,
Quinn

The fish tank right now:

It might have been the tap water. Back when I lived in the city if they did construction or sewage work near us the water would turn colors and we had to get it bottled. If you live in a rural area it could still be a problem with tap water, temperature, or maybe a chemical that your tests don't account for. Im not a water master nor a fish master but it could have been any number of other things too.

Did you distribute the dechlorinator around the surface of the water before starting to refill the tank? I do that and then I fill the tank using a python water changer and use a stirring motion to be sure dechlorinator is thoroughly mixed as I fill the tank. After a minute of doing this, I then lower the filling hose toward the bottom of the tank and just rest the hose against the side of the tank and sit back and watch that it doesnt overflow. I match the tap water to the temperature of the tank. I have been doing it this way for years without issue. I try to stay away from directly inputting water into a fish's path.

Sorry about your fish loss.

It was the tap water for sure. You never know when your tap water could have chlorine in it. That's why you should always use dechlorinator, even if the water company claims that it is "chlorine free". I realize you said that you added it in while filling the tank up, but that's NOT how you're supposed to add it to the water. Most bottles will say to mix the tap water and the liquid dechlorinator in a seperate container. This is the only safe way to do this.


(Also, why is your water level so low?)

I can think of two possibles here. First, as suggested above, there was a problem with the tap water. This may not have been just chlorine/chloramine related, but something else. Have you asked the water authority if any changes were made, say different substances added, or more of "x" or whatever? I agree that filing directly from the tap might have been problematic, but only if something had changed. I fill directly from the tap and have for 30 years now using a Python, and even with high chlorine a squirt of the conditioner when starting to refill has always done the job. But this would not be the case if "x" occurred.

Second possible poisoning from the disturbance of the substrate. I'm not sure lava rock would prevent anaerobic pockets, and if such were suddenly exposed it can cause death as rapid as described here. But around plant roots which are presumably releasing oxygen as a by-product of photosynthesis one would not think it likely, but who knows.

quinnARIUM said:

Temp remained the same at around 82 degrees....

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quinnARIUM said:

I always get the sink to close to the correct temp then fill up the tank

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What do you mean "correct temp" ? Is it the same temp as tank water ?

If filling with a hose, you should be dosing the dechlorinator for the full tank size, not just for the amount of water added.

Thank you everyone for all of the feedback! I agree that it was probably something with the tap water. I think I am misunderstanding how to best dechlorinate the water as it comes into the tank. Does dechlorinator have somewhat long lasting properties? Should I add the dechlorinator before filling instead of after?

Fishmanic said:

Did you distribute the dechlorinator around the surface of the water before starting to refill the tank? I do that and then I fill the tank using a python water changer and use a stirring motion to be sure dechlorinator is thoroughly mixed as I fill the tank. After a minute of doing this, I then lower the filling hose toward the bottom of the tank and just rest the hose against the side of the tank and sit back and watch that it doesnt overflow. I match the tap water to the temperature of the tank. I have been doing it this way for years without issue.

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Chlorine/ Chloramine poisoning caused by adding chlorinated water to the aquarium. This is why you should always dechlorinate tap water before adding it to an aquarium with livestock in.

Water companies can and do increase the chlorine/ chloramine levels in the drinking water at various times of the year. These can include:
If the weather warms up.
If work is done on the pipes.
If pipes are damaged (possibly due to freezing or earthquake).

The water companies do not tell you they have added more chlorine/ chloramine, and you do a water change using the normal amount of dechlorinator, and the fish die shortly after the water change.

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The safest way to dechlorinate water for an aquarium is to fill a large plastic container with tap water. Then add enough dechlorinator for that volume of water. Vigorously aerate the water and dechlorinator for at least 5 (preferably 30+) minutes. Then use the water in the aquarium.

Aerating the water helps mix the dechlorinator through the water so it has time to come into contact with all the chlorine/ chloramine molecules. It also helps to get the dissolved gasses in the water back to their normal levels. When water is under pressure like in the water pipes, the dissolved gasses in it can come out and you might end up with lots of carbon dioxide in the water but no oxygen. Aerating the water for 30 minutes or more, helps get the dissolved gasses back into equilibrium so it is safer for the fish.

If you have a big fish tank, you can use a clean plastic wheelie bin or large plastic storage container to hold water and to aerate it while you gravel clean and drain the tank. then use a small water pump and hose to pump the water from the container into the aquarium.

How much Dechlorinator did you add. Did you measure it for your tank size. Or did you just give it a good squirt. 50% water changes is the preferred way on this site, and there are lots of people to help you.

quinnARIUM said:

Thank you everyone for all of the feedback! I agree that it was probably something with the tap water. I think I am misunderstanding how to best dechlorinate the water as it comes into the tank. Does dechlorinator have somewhat long lasting properties? Should I add the dechlorinator before filling instead of after?

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I very rarely take a different approach from Colin, but on this issue we do things differently. But let me say first off that if you are more comfortable following his approach of preparing the water external to the tank, there is nothing wrong with that. But I would do it differently, as I have been doing for 30 plus years now, ever since I acquired my first "large" tank that needed a "python" rather than buckets for water changes.

And before getting to the method I use, it is obvious that whichever method you use, sudden unknown changes to the tap water are still going to cause problems.

When changing water in smaller tanks, using a bucket can be easier (provided you can carry them; I could never have done this during the six-plus months of my recovery from cancer surgery last November), and it is simple to add the number of drops per gallon the conditioner requires. A 3-gallon bucket for example, which is the basic size I use, requires three drops of the API Tap Water Conditioner. When using a Python and filling direct from the tap, I add the conditioner as the refill begins, directly into the tank. If I am changing 1/2 of a 90 gallon tank, I know that this is roughly 50 gallons (substrate and wood/rock displaces some of the water) so I add conditioner for 50 gallons once the refill begins. Except for the two occasions when I forgot to add conditioner, I have never had any problem doing this.

I do not like using more of an additive when it is not necessary, so I do not add conditioner for the full tank volume (unless changing all of the water obviously). Quality conditioners like the API and Seachem will do the job without overdosing.

Avel1896 said:

What do you mean "correct temp" ? Is it the same temp as tank water ?

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yes try to get the water your putting in at a similar temp to the tank water

too much water conditioner is always safer than too little or none at all too

The instructions on the seachem prime bottle says to add the dosage required for your full tank volume if adding tap water directly into the tank. If using buckets you can just dose each bucket for volume of the bucket.