Is the damage done to plants by too much salt permanent and pretty
much instantaneous or will they recover if you drop levels back down?

The reason I ask is that I'm concerned about the possibilities of
parasites in my pond, as mentioned in my "Looking for Pond Health
Tips" post. Is a possible treatment for that to gradually raise the
pond's salt level to .3% and hold it there for a day before gradually
bringing it back down, or will that not kill "the bad things?" If it
would kill the bad things, would it also kill my plants, or would they
recover once the salt dropped back down to .1% a few days later? And
would a .3% concentration harm snails, tadpoles & frogs?

I've never heard of anyone suggesting this approach, so I'm assuming
there are good reasons not to do it. I'm just curious what they are.

Thanks,

Dave