The Mantis Calcium Reactor CR100 is designed to maintain optimum and stable pH levels for corals, whilst balancing calcium, alkalinity, magnesium and trace elements. CR100 is ideal for small to medium aquariums up to 500ltrs. Features: Controllable DC Tornado 4000 pump - Reverse flow and CO2 recirculation design - Auto Fill bubble counter - Effluent control valve - Easy maintenance - Internal or external installation.