Serious question, as daft as it might sound - do they have to chlorinate the water to stop stuff growing in it? I'd expect it'd be about "swimming pool" warm so just great for all sorts of manky algae growing.
I bet there's some good chance of getting wacky extremophiles though!
edit: sorry for being lazy, I scrolled a bit more and found it.
Hot spring baths usually top out around 42-43C