Seachem recommends that the UV be turned off during Cupramine treatment.
The UV disrupts protein molecules and thus would disrupt the Cupramine formula. This exposes the copper and makes it more lethal/poisonous to the marine organisms. In essence, the person turning a UV on this product is converting it to a free copper, like copper in a copper-salt treatment.
I would use cupramine and keep the level at .5 for the full treatment. NO UV during treatment