1. The best way to treat ICK is with Hyposalinity. You will need to drop the salinity down to 1.009 slowly.
2. You will need to purchase a refractometer to accurately measure the salinity.
3. You will need to remove the live rock and place in another container or something. All shrimps, crabs, snails etc should also be moved. Use the same tank water from the main tank and try to put a powerhead in there to circulate the water.
4. Once the tank is down to 1.009, leave like this for a min of 4 weeks but 6 weeks is preferred.
5. Good luck and start asap.
Anthony