Thank you for your question, Ripped Tide. We hope to be able to address this for you. Cupramine is a very effective copper medication, as it kills parasites, but is still very safe for fish. Cupramine contains an organic complex which leaves the cupric charge (Cu2+) fully active. This amine complex inhibits copper absorption by fish, but does not interfere with its action against parasites.
When utilizing UV while treating with copper, the UV can actually reduce the 2+ charge to 1+, which is extremely toxic to fish. This is why we recommend turning off UV when employing Cupramine in the system. We hope that this information was helpful, Ripped Tide. Please let us know if you have any further questions.