Hmmm...that’s good info and it kind of upsets me to read that as well. Sorry about your fish man. I’ve kept fish for 3 decades and never had issues after a water change. In fact, the only issues were when I first started out fish keeping and didn’t do enough of them. Now that I switched to Safe, I’ve lost over 22 fish in short order...17 in one shot this last time.
I also double dosed Safe per instructions just to be cautious. Shortly after the water change my plecos we’re going nuts, panting with cherry red gills, and banging themselves all over the place and eventually flipped over. Mind you, this was my backup colony of L134 and L46 plecos, some nice angels from Steve Rybicki, and some rarer cories. Pricey losses and fish I raised out for a long time.
I talked to an Marine and fish biology professor this weekend and he says it’s likely chlorine exposure. He said, the cities sometimes dose heavy at different times of the year. That makes sense but why have I never had these issues before when I did water changes? Safe was a great, cost effective option but I’m going back to Prime. I don’t pretend to know exactly what happened but can only share my personal experience. I’m just not using Safe anymore...can’t trust it. The first time could have been an odd occurrence but this second experience, which went down the same way, seals the deal for me.