Copper is a more directed approach when dealing with either Cryptocaryon irritans or Amyloodinium ocellatum, especially if you cannot detrmine properly which one your treating. Malachite green and aldehyde treatments are not nearly as effective or prefered. The Cupramine is also much better tolerted by the fish. PARA has it's uses but it's a matter of which is more effective and least damaging to the fish. Both being poisons, it's a matter of the lesser of two evils so to speak.
If you know for sure it's Crypt, hyposalinity is your best option.