Longest Possible Safe FW Dip?

[marie]

The longest (and only time) I've been able to leave a fish in fresh water was about 90 sec's.....I thought I had killed it

I am in the same boat with choosing healthy fish. I am a long ways away from the nearest fish store and have to rely on someone else to choose my fish so I can't afford to not quarantine, especially after I lost half my stock to marine velvet.
That said, I quarantined and treated my Achilles successfully for 8 weeks

Here's Doofus 6.5 yrs ago, recovering from fresh water dipping and copper treatment