my oscar had ich, he was kinda large (7"-8") and I heard it was common for large O's to get it when moved from tank to tank.
I did aquarium salt and temp at about 85 and it was gone in 2 days. I swear by the salt treatment now.
Also would like to add that I used rid-ich first and after a week didn't see any significant changes. I stopped after my mother decided to feed the fish and covered the entire surface of water with pellets, so I did a massive water change and netted all the fishfood out and had to put the carbon from teh filters back in. Thats when I used salt and it got rid of the ich so fast.
I did a tablespoon per every 5 gallons. The next day I would add a bit more, and then a bit more.
I know that a ton of freshwater fish are more tolerant of salt than people let on. At the LFS near me, they toss cups (yeah like 8oz) of salt in to some of their 40 gallon tanks. They say it helps them heal up faster, and they have a lower mortality rate because of it. So I say go for it.