First PWC results in 5 dead fish

[jlanier]

So I did a fish cycle of a new tank (38gal) with 9 danios. Everything has been going perfect; all fish seem healthy and fine, ammonia, nitrates, and nitrates finally where they should be. Then today I do my first PWC with my python, 30 minutes later 5 dead fish. Any ideas on what could have went wrong? Should I have removed the fish from the tank during the change?

 

[ErnieB]

did you conditoner the water before putting it in the tank? ( dechlorinate ) or what about the temperature of the new water? If it was a large water change and the temperature wasnt close that could have affected them as well.

 

[Markstanfill]

I would second large temperature drop/ascent. Chlorine will not kill fish that fast, my leftover fishing minnows can attest to that. Had to have been a big change though, on the 10 degree or more market. And if you are using a python, be sure to treat the entire tank volume with dechlorinator prior to adding water if you dont already. Could also be a large PH swing, but once again it would have to be on the order of more than probabbly 1-1.5 points in either direction.

 

[jlanier]

I thought I had the water temp pretty close to the tank temp. I used a therm. to get it as close as i could from the running tap. Two more died later in the night, so 7 of 9 total.

So I guess for the next pwc is it advisable to move the fish to a temp tank with water from the main tank while doing this?

 

[rive1404]

No need in taking the fish out, it will just stress them even more. All you need is a bucket, a thermometer, and a heater. Or if the water is too warm, just let it sit for a while until it's room temperature.

Try testing your water, too. If you're using tap water, you may need to check with your water dept. to see what chemicals they toss in.

Sorry about your fish

 

[WhiteDevil]

get another glass aquarium thermometer and use that when adjusting the water temp at the sink prior to filling the tank. I do PWC's like this with no issues, I run 3-4 degrees cooler to entice the angels to breed but just get the temp close within 2-3 degrees cooler never hotter as the tank temp now then add conditioner then the python end flowing water.

Sounds like either Ph swing, water temp hard swing or under/over conditioned water.

 

[jsoong]

Might be a pH swing. During cycling, tank pH can drop, and the water parameters may be far off from the tap. <Also your water co might have changed protocol & started liming the water or something so the tap is way off from before.> Maybe you should check tank pH & KH & see how close that is to tap.

If you match the tap water temp to tank with a thermometer, it is unlikely to be temp swing. Even if the thermometer is way off, you can still match the tank temp regardless of the actual number.

 

[T Dawg]

Then today I do my first PWC with my python

What was the % of water changed?
Did you add dechlorinator both before and after the addition of the water?
Have you tested the water,and if so could you post the numbers?

 

[jlanier]

I did about a 20% pwc. Stats before and after the pwc are the same
Ammonia - 0
Nitrate - ~3.0 ppm
Nitrite - 0
Ph 7.2~

Only thing I can think of is something must have gone wrong with the water temp coming from the faucet through the python. Either the handle was altered which changed the temp or something.

 

[Blueiz]

Did you use dechlorinator before afding the water to the tank? If so, what is the name of it? A 20 percent water change isn't going to affect the temperature so dramatically that it kills fish unless it was boiling hot and the fish were close to the water flowing in the tank.

 

[joy13]

Could it be something to do with the city water, have they added anything lately?

 

[T Dawg]

That is odd the Nitrate did not change at all after a 20% water change.

What brand of dechlorinator did you use, when did you use it, and how much did you use?

 

[supradupafast]

Hmm.. I second what BlueIz said.
With 80% or so of the old water still in the tank, kinda hard to alter the temp unless you were using Frozen or Boiling water. When filling with a Python, I usually can feel the temp and compare with my finger (Tank - Tap) and adjust from there. I also add my water conditioner (I use API's) while I fill. I find it dilutes faster while there is water movement from my Python. So here is what I think could have happened. Depending how long your tank had been running with a Bioload in it, perhaps when you pulled the Python out of the water and the water in the Tube part falls back into the tank, it may have disturbed the gravel and release / polute the water causing a Ammonia Spike and the fish being directly affected by this. Now, this may not be the case, but JMI.

 

[Viper]

I actually just use my hand as a gauge for the temperature as I can tell relatively what the temp should be. Since I use this method and have had no problems with fish dying, it sounds like it has something to do with the chemical parameters of the water that was already in the tank and the water that you were adding.

 

[jsoong]

With only a 20% pwc, I think it unlikely that the deaths are caused by water parameter change or temp change. Danios are pretty hardy guys & a 20% drift in water parameter (that is assuming that the change water is totally screwy, which it does not appear to be) should not have that drastic effect.

Is it possible that the python is contaminated? perhaps with soap, oils or pesticides, etc. Did you rinse out the python before first use?