The API® COPPER TEST KIT allows you to easily and accurately monitor copper levels to maintain copper-based fish treatments at therapeutic levels, and tests copper levels from 0 to 4 ppm. The kit measures both free and chelated copper, and is for use in fresh and saltwater aquariums, or with ponds. Copper – a treatment for many parasitic infections – must be monitored in an aquarium or a pond. The copper level can drop too low for the treatment to be effective, or can increase to a point that is detrimental to fish health. Copper is likely even present in your tap water.