anyone else in tucson having issues during water changes

did a small water change on one aquarium yesterday and now my fish are back to swimming at the top gasping for air , it did this on my last water change about 2 or 3 weeks ago. i am wondering if anyone else here in tucson has been having issues lately

That is very strange... how large of a change did you do?

today was about 15-20 gallons in a 125 gallon aquarium, would a small increase in nitrates from the tap water cause this? i had ordered a large bottle of api tap water conditioner, but didn't realize it did not remove nitrates. this is the only change from water changes before this.

Normally gasping is an issue with the oxygen in the water.

A few things I could think of are...

1. If chlorine in the water killed off bacteria the death would spike CO2 and deplete oxygen. Since you mention water conditioner I highly doubt that.

2. The temp of the water going in is too high and carries less oxygen. If you do you water change and just about match temps that should cross this off the list.

3. Some people report that their tap water in the afternoon is very low in O2. Depending on the time of the change it would be worth trying an AM water change.

4. Surface aggregation. If the water is low in O2 you may need to stir up the top of the water if you're not already to increase O2 in the water.
Some water is just low in dissolved O2 levels especially if it is very hot outside. The only real way to solve this would be to increase surface aggregation in the tank after adding the water OR to have a bubbler running in a water holding container to allow the oxygen levels to normalize before adding it.

the water comes out around 76 degrees here, so its not much lower then what i keep the tanks at. i have three twelve inch air stones going pluse the surface has a but load of agitation. this problem has started occuring the last two water changes, never occured in the three years this tank has been running before that with the same set up.

You said you recently switched your water conditioner?

I mean when nothing else changes you really have to look to the small things.

didn't realize that the one i ordered didn't have something to remove nitrates in the tap water.

Wouldn't think nitrates would matter. I mean the water change is done to lower them anyways.

perhaps you can call the water company and find out if there was something they changed in their water treatment. I had this happen to me a few water changes ago and lost a fish, now I just let my water sit for a longer period of time. Maybe they changed up their process that you don't know about.

i went online and looked at what they say the water is coming out of the tap as, between 7.4 and 8.0 ph temp of 76.3 1.8ppm on nitrates, .95ppm chlorine that is the latest update for this area.

did you happen to rinse out your filter as well? It sounds like a dissolved gas issue, even though it's only what, a 10-15% water change? I'm stumped as much as you are.

rinsed off removable parts

Sometimes the rinsing in conjunction with a water change would trigger the dip is gas levels. That's what happened to my tank.