Good morning, and first of all, happy new year to everyone!

I have a quick question: How much aquarium salt is acceptable to plants? If
my fish have a mild case of ich, i usually like to treat it with aquarium
salt (usually about 1 tsp for every 15gal) I am leary about using aquarium
salt on my tank since it is heavily planted, but I am not really sure how
salt interacts with plants... Any ideas?

Also, just out of curiousity, what happens if the co2 levels in your
aquarium reach a little over 40 ppm? I was avobe 40ppm a few days ago,
and i think it was stressing my fish out, but i brought it back down. (right
now its about 15ppm)