GRRR!! It is so frustrating to me that so many goldfish suffer because of the ignorance of "sales" people. If you dont believe me fine. Got to this web site and it will back up everything I told you.
http://www.koivet.com/html/articles/articles_details.php?article_id=22&category=17&name=Diseases
Stop using formalin, salt and heat are all you need. You need BOTH because there have been reports of heat tolerant ick. If you dont raise the heat the icks life cycle can be days, even weeks and will kill your fish before they start to die off.
The gills of your fish turning red is a very bad sign. You need to start this treatment
ASAP to have any chance. The ick is infesting the gills and basically slowly suffocating the fish. I know 1 tablespoon sounds like alot, but its really not. I do not recommend using formalin because it can be very easy to OD and kill your fish with. Plus its very harsh on fish that are already weak.
If youre serious about keeping koi and goldfish, I highly recommend you read every article on the website I gave you, and also buy the book Fancy Goldfish : Complete Guide To Care And Collecting by Erik Johnson and his other book, Koi Health and Disease. These should be your bible to koi and goldfish keeping.
I know its frustrating when youre getting alot of different info, and dont know who to trust. Goldfish are a big part of my life, and I'm telling you to trust what I'm telling you and trust that website. I hate to hear of so many goldfish suffering that could easily be saved or the problem avoided altogether because of common myths and just sheer ignorance.
HTH