Oh, good point, I'd forgotten about that. Ugh...it's just gross, gross stuff.
Rickey is right though, it's in a lot of meds...but, if you look around, you can usually find an alternative that *doesn't* have it in there.
I avoid formaldehyde, copper, and the "fix" products. All of them are NOT good for fish, and are usually older products. The copper was thought to be a "miracle chemical" and people were putting big sheets into their aquariums...until they realized it was actually killing the fish over a period of time. (Rather like how cocaine was the fix-all for everything in people until they realized that it was actually massively addicting and had serious negative health consequences.) And formaldehyde has already been established as not for living tissue. As for the "fix" products, there's debate about those. Some people swear they're awesome, other people say it can hurt their labyrinth organ. I haven't used it, don't have experience with it, but I'd rather use something that I know is safe rather than something that has a sketchy track record.
The Jungle product is safe, not top-of-the-line like Prime, but definitely safe, and it'll dechlorinate your water and help their slime coat. And it's cheap. :)