HELP!! Salt treatment???

Okay, so here is a somewhat long story....

As of right now (3/19) I do not have any turtles. I just ordered 3 cb 08 turtles from turtleinc.com and am expecting their arrival next week (probably tues-wed).

HOWEVER, I just noticed that some of the goldfish in their soon-to-be-home look lethargic and might possibly have some ich/ick (however you spell that). After doing some research, the recommended treatment is to add 1 tablespoon of salt per 5 US gallons and raise the temperature (which I have to do for the turtles anyway). I don't want to use any medications because I have live plants (and I use carbon in the canister filter... which is a pain to take out b/c of the setup underneath the aquarium....)

My questions is, will this salt harm my turtles? I can put them in a temporary 29 gallon aquarium for a little bit, but I'm afraid I'd have to do a complete water change (75 gallons) to get rid of that salt when I wanted to move them into their home...

Does anyone have any ideas on this? I dont want to hurt my babies!!!

Btw, the species of turtle are 1 eastern painted, 1 ouachita map, and 1 midland painted (all cb 08 hatchlings, about 1-1.5" in size).

Thanks in advance for any help!