Water Change Fish Dead

[Stephan]

My nephew inherited his stock from a friend. In his 20 gallon were I believe a rainbow shark 2 red tail sharks and several tiger barbs. I'm not sure what else. He went home today and did about 50% water change which was more than usual. He said when he put in the first pitcher of replacement water the biggest tiger barb was acting frantic and then upside down. He continued to fill Within 2 minutes almost everything was dead. He moved a red tail to another non cycled tank for emergency. It lived about 20 minutes and died. The red tail he left in the tank is the only fish that survived.

Like his crazy self he put in the dechlor after filling. But that wouldn't just kill fish that fast like that would it? He also said when he dumped the water in and it disturbed the gravel it basically made the whole tank dirty. He does not vacuum.

So I'd like to be able to figure out some ideas of what might have gone wrong so he, myself, and my friends don't end up repeating whatever the mistake was.

Thanks.

 

[KittyKat]

What were the water parameters? Was the water he was using cold? What sort of filter do you run?

It could have been the new water, but more likely to have been a combination of things.

 

[This Old Spouse]

Not only were the poor fish subjected to water full of chlorine, but if there's no vacuuming going on, they were also breathing in all of their own poo that was churned up during the water change.