It's a bit like being burnt alive apparently - not something I want to do to my fish!
Salt isn't used so much these days, plenty of non-salt based treatments on the market. I often use aloe vera based tonics which work well for me. Makes their fins glossy too
I've been soaking a piece of vine (normally used in vivariums) for a few months and only recently has it soaked up enough water not to float - now I will boil it a few times and should hopefully have very few tannins. Bog wood is terrible for tannins if not soaked well first.