Space-saving calcium reactors allow versatile, in-sump or out-of-sump installation. Hydor Performer CR Calcium Reactors boast user-friendly features to make calcium supplementation in reef aquariums simple and convenient. Performer CR calcium reactors can be installed in-sump to reduce under-cabinet clutter. Easy-fill design allows top access for hassle-free media re-fills. Includes precision bubble counter to help monitor CO2 injection rate within calcium reactor chamber. Reactor media, supply pump, and CO2 system sold separately.