Goldfish clamping fins after water change

[Ellie11]

I’m asking for a friend. He has a group of goldfish in a big tank for two years. He said he did a water change and all the API readings before and after were good. He says he conditioned the water right and used about the same temperature for new water, but suddenly they all clamped their fins and he changed more water. He is certain his hands were clean and nothing got into the water. He is desperate for help. Any ideas?

 

[Back in the fold]

When I read posts like this I wonder when was the last time a water change was done. Was it last week or a couple months ago ? Fish can get used to bad water and when you freshen things up they react poorly like the fish described here. When fish get regular water changes they never do much different. It's when there's a big sudden change that they change behavior.

 

[Ellie11]

Good point. I’ll ask him. Thanks

 

[Archerfish]

If you can get your hands on some historic aquarium books, they will discuss 'old water' and how much that golden hued water was cherished back then. Some aquarists traded and even sold their 'old water.' The books also mentioned the disastrous effects of introducing large amounts of 'new water' into a tank. This of course is an example of two extremes but reinforces what @Back in the fold is sharing which sounds like spot on advice. This might be a great opportunity for your friend to join this forum!

 

[Ellie11]

What fascinating info! I had no idea!
Hey, man, I have some golden water from one of the tanks in the back room I forgot about. I’m running a two for one sale. For the price of one gallon of water you get two! Act now. Supplies are limited.