Parasites /irritants in my tap water?

[squirrilah fish]

I did two water changes last night between two tanks, one being a quarantine tank.
Today the fish in my QT tank is scratching, he's not a new fish, he's been in the QT 3 weeks waiting to be sold, and is now acting like he has a gill fluke or something.
In my other tank the fish got really pale, I have fish breathing very rapidly, scratching. Could something in my tap water be causing this.

I use Prime.

Test in both tanks where
PH 7.8
Alkalinity -ideal
Hardness 150 (hard)
Chlorine - 0
Nitrite - 0
Nitrate <5
Ammonia 0

 

[fishman888888]

How big of water changes did you do?

Perhaps your gh/kh dropped really quickly and stressed the fish

What do you use to add your minerals?

 

[squirrilah fish]

It was a 33% change. I don't use anything but prime and tap water. Which is hard and alkaline. I've used the same tap water for years. And I have noticed there seems to be some irritation/ scratching during the winter to spring, and fall to winter seasons. I'm wondering if there's just significant changes in my local water table. Of it's possibly something else.

 

[Delapool]

I've noticed a difference in kh between winter and summer. Not sure on gh as my test is out of date.