Hyposalinity at 12 to 14ppt salinity (not SG) works well for ich. I would not use any copper other than Cupramine, especially on copper sensitive fish such as puffers. You should test the copper level twice a day and you will need a different test kit to measure Cupramine. A RedSea copper test will work well enough. It only measures to .4ppm, but that is actually high enough with Cupramine (Seachem suggests .5ppm).
Terry B