Salting tank safe for inverts?

I have a 20 gal tank with 4 guppies, 2 black chin livebearers and a million inverts, including pond snails, MTS, ramshorns, nerites and yellow shrimp. All of my animals are equally loved by me and I wish to do none of them harm, even the pond snails.

I'm pretty sure my snails/inverts are harboring a parasite that is harming my fish. I want to salt the tank to try to help the fish fight off the parasites. I know 2 female guppies will probably not make it, but my other fish still have a chance. This might be a shot in the dark, but I want to try and save everybody. Is adding salt safe for the invertebrates? How much salt could be used?

http://www.aquariacentral.com/forums/showthread.php?t=159432

Refer to this thread here. The parasite/fungal disease/unknown is called Ichthyophonus hoferi. I am 200% positive this is what is hurting my babies. And it transfers from snail/copepod----> fish--->other fish via eating poop or the tissue of the infected organism. There is no information I've found on successful treatments, however I need to try stuff out for my fishies sake.

I want to treat the tank with aquarium salt and an anti-fungal medication, hoping to prevent the normal-acting fish from becomming sick. Who knows, they might already be infected and not showing symptoms.

I currently just moved the 2 visibly sick fish in a separate hospital tank. The tank is going to be salted in 1 hour after the remaining fish is better acclimated to her surroundings. As soon as my boyfriend gets home from work (4pm), I'm going to get an anti-fungal medication and treat the hospital tank.

Depending on your guys' recommendations, I am either going to treat the entire main tank (inverts and all), or procure a 2nd hospital tank to treat the normal-acting fish separately from the main tank.