📖 Overview
Copper is a paradox. At 0.15-0.25 ppm it kills marine parasites - the gold standard for ich and velvet in fish-only tanks. But it kills invertebrates, corals, and beneficial bacteria at those same concentrations. Copper treatments are done in bare quarantine tanks, never in the display tank. Once copper is in a tank, removing it is difficult - it binds to substrate, live rock, and equipment.