Hyposalinity is the best treatment choice for ick. Do you have a FO tank [meaning no live rock, live sand or inverts]? If so, you can safely perform the hyposalinity procedure in your main tank. If you will do a search here, or visit our Archives and look for TerryB's thread on ick, you will find many many many discussions on how to preform the procedure. If you have other living organisms in your tank besides fish, you will have to perform the procedure in a separate hospital tank.
Your other option would be to use a copper treatment. I would not put any medications, including copper in your main tank. You will need to use a separate hospital tank. Copper treatment is also discussed and you will find the info by using the search feature.
All fish, whether they are showing signs of ick or not, will need to be treated as, once exposed to the parasite, fish are infected or carriers.
Let us know if you need more help.