Water change last night..woke up all fish dead.

I have a 55 gallon fish tank. I set it up last December. It is fairly established. All parameters have been good I have lost a fish hear in there but the whole time I've had it I think I've only lost 3 or 4 fish. I have been super busy with work so I slacked on water changes. It's been almost 3 weeks. So I did a 40 percent change last night. Woke up and practically all my fish were dead..the ones I could find

15 dead neons
2 Dead Cory's
2 dead zebra Danios
1 dead clown pleco
Can't find my bristlenose pleco.

Why did this happen...

 

Oh no. That stinks. So sorry for you losses. Did you add the declorinator? I'm still pretty new to this. So I really not sure what could have happened.

 

. So sorry to hear this! Did you test your water parameters before the water change? Sometimes dropping nitrates too fast can send fish into shock.

 

Did you check temperatures? Did you add the dechlorinator? If you used a bucket or container could it have been contaminated with something.? I have never heard of that many fish dying from a water change like that . I am so sorry for your loss. can you check your water parameters from the tank water and your tap water both. There has to be a reason but it might be very hard to figure out what happened. Alison

 

I had just run out of prime halfway through
I will check water parameters when I get home but I did check ammonia and nitrite and had neither

The only fish that stayed alive were my 2 angels a pearl gourami and my blue ram. None looked very good. What do I do now. Financially it'll be about a month or more before I can get more fish in there. What do I do with my tank in the meantime to regulate it. Where could my missing pleco be

 

Add a dechlorinator like prime, make sure you didn't shock the temperature. I'd get your water tested from the tap as well. So sorry to hear about this. Did you stir up a lot from the gravel? Did you gravel vac?

 

I'm sorry for your loss : (
Hopefully you find out what caused it

Maybe try some stress zyme to keep the filter busy? I'm honestly not sure though, sorry

 

Check under things and inside any ornaments for him, also check around the tanks on the floor as he could have gotten out to escape the water unless you have a good tight top. Alison

 

It's possible that when you did the water change, you disturbed a pocket of anaerobic gas that has built up in the substrate. This releases a plume of toxic gas into the the water which essentially poisons the fish. This happened to me once when I hadn't disturbed my substrate in awhile and then I went over board with the gravel vac and released all this built up gas.

 

It's possible that when you did the water change, you disturbed a pocket of anaerobic gas that has built up in the substrate. This releases a plume of toxic gas into the the water which essentially poisons the fish. This happened to me once when I hadn't disturbed my substrate in awhile and then I went over board with the gravel vac and released all this built up gas.

I have never heard of this but it is possible as I did a very through water change

 

I have never heard of this but it is possible as I did a very through water change

In a nutshell, waste buildup in the substrate causes a release in these toxic gasses that remain trapped until they are disturbed. This normally isn't an issue in smaller amounts if you stir up your substrate from time to time but a pocket of undisturbed gas can build up a lot over time, especially if the substrate is on the deeper side. A way to prevent this is to make sure you agitate the substrate regularly. MTS can do this for you since they like to burrow but this is easily done with a bamboo skewer; just poke it into the substrate to allow the gases a channel to escape.

 

In a nutshell, waste buildup in the substrate causes a release in these toxic gasses that remain trapped until they are disturbed. This normally isn't an issue in smaller amounts if you stir up your substrate from time to time but a pocket of undisturbed gas can build up a lot over time, especially if the substrate is on the deeper side. A way to prevent this is to make sure you agitate the substrate regularly. MTS can do this for you since they like to burrow but this is easily done with a bamboo skewer; just poke it into the substrate to allow the gases a channel to escape.

What is a MTS?

 

In a nutshell, waste buildup in the substrate causes a release in these toxic gasses that remain trapped until they are disturbed. This normally isn't an issue in smaller amounts if you stir up your substrate from time to time but a pocket of undisturbed gas can build up a lot over time, especially if the substrate is on the deeper side. A way to prevent this is to make sure you agitate the substrate regularly. MTS can do this for you since they like to burrow but this is easily done with a bamboo skewer; just poke it into the substrate to allow the gases a channel to escape.

I thought this was not an issue if the substrate (sand) was not greater than 2 inches deep.
Out of curiosity, when this happened to you did you have deep substrate? did you have sand or gravel?

 

I thought this was not an issue if the substrate (sand) was not greater than 2 inches deep.
Out of curiosity, when this happened to you did you have deep substrate? did you have sand or gravel?

I do think there are places the gravel is more then 2 inches deep

 

What is a MTS?

Malaysian Trumpet Snail

I thought this was not an issue if the substrate (sand) was not greater than 2 inches deep.
Out of curiosity, when this happened to you did you have deep substrate? did you have sand or gravel?

I had shallow and deeper areas. I actually had gravel which I thought would allow enough space between each of the particles to allow the gas to diffuse slowly on its own but what I hadn't counted on was the fact that the gravel I used was specifically for planting so it was nutrient-rich. Having all of those organic compounds already in the gravel essentially beefed up the amount of gas that had already accumulated and exacerbated the problem so much so that when I finally went in for a thorough gravel vac, I saw a literal plume erupt from the substrate. Of course my inexperienced self thought nothing of it until I started losing fish left and right.

 

My guess would be too fast in the drop of nitrates as well especially if you had gone 3 weeks without a water change. When it's been that long without a water change and then you suddenly do a large one, that could be fatal. It would have been better to do some smaller ones gradually.

 

My guess would be too fast in the drop of nitrates as well especially if you had gone 3 weeks without a water change. When it's been that long without a water change and then you suddenly do a large one, that could be fatal. It would have been better to do some smaller ones gradually.

Google "Old Tank Syndrome"... since I think this is what el337is referring to. How much did your nitrates usually build up in a week? Somehow I assumed Old Tank Syndrome would occur over months, but I (thankfully) don't have experience with this. I think Aquaphobia may have experience with nitrate shock... at least given some fish he rescued a while ago?

 

Could also be pH shock if your tank water is vastly different from the new water being added, i.e. your tank water has a higher pH than your tap, then doing a large water change is fatal.

Here's a thread on the importance of a good water change schedule and the negative effects on going a while without one, including links to OTS.

 

Luckily I've only killed one fish that way, the next two times I encountered crazy high nitrates it was in rescue situations and I was able to bring the nitrates down slowly over a few hours to allow the fish to acclimate.

 

My guess would be too fast in the drop of nitrates as well especially if you had gone 3 weeks without a water change. When it's been that long without a water change and then you suddenly do a large one, that could be fatal. It would have been better to do some smaller ones gradually.

I had no idea that a swing in nitrate levels were that harmful, I learn something new here every day!

 

I had a similar thing happen to me (except I wasn't behind on water changes). It turned out that I have water with low gH & kH and apparently my pH crashed and the ammonia all turned into ammonium (which is not toxic). This I was told made made my ammonia converting bacteria become dormant. But once I did a water change, the ammonia all turned into ammonia, my ammonia converting bacteria woke up and started producing tons of nitrites. My nitrite converting bacteria all starved off since the ammonia converting bacteria hadn't been converting ammonia into nitrites and I suddenly had a huge nitrite spike overnight and woke up to find almost all of my fish suffocated.

 

So sorry that's terrible. You said you ran out of Prime half way through... how much did you use for the 40 percent change? Trying to figure out what happened. So sad.