FWIW......I had the exact same problem when i dropped my tiny hippo in my 75g.
She developed ich after a couple days. I freaked out and started reading on line what I needed to do and what products i could use. Use this product, empty the tank and run for 8 weeks, do a freshwater dip yadda yadda yadda.
I may have gotten super lucky, but I did none of these. I made sure my water quality was pristine (tested every single day-PH, Salinity, Trates, Phos), always made sure to have seaweed w/garlic extract on the clip available to her and made sure to minimize temp fluctuation! The clowns and firefish never got it, so i figured i wouldn't go too aggressive with a treatment. After about 2-3 weeks, she cleared up and hasn't been back since. She's actually doing very well these days and is a gorgeous deep blue.
Like i said...maybe I just got lucky, but the non-aggressive treatment worked for me.