Tony, what kind of fish are you treating? Are they scale-less fish? It helps for treatment advice.
Hyposalinity I like better than Copper any day. More natural is better. However I would use the darkness & transfer method also with Hyposalinity treatment to be the most effective. Let me know if you want more info on how I do that.
to answer your question on Hyposalinity....here's steps
In Hyposalinity the normal salt content of the tank is reduced by over half, that is from normal 35 ppt to 16 ppt, which corresponds to a specific gravity of 1.009. The treatment is done in stages. On day one RO/DI is used to replace hospital tank water till specific gravity falls to 1.022, day two it is reduced to 1.018, day three 1.014, day four to 1.009.
I will warn you, once you hit 1.018, you might see a nitrate/ammonia spike. That's why its important to adjust the salinity down slowly. Also by lowering the salinity this way it will prevent your fish going into osmosic shock. Like a invert would do if you didn't match the salinity when first introducing it to your system. I have dropped it faster with no shown effects to the fish.
Hope that helps.
