A simple digital controller is used to adjust the effluent flow through the reactor and thus raise or lower the alk. The CO2 is controlled for you WORRY-FREE, so that you can spend your time how YOU want. Our A.C.R. features an economical CO2 recirculation system, so it uses 50% less CO2 than other reactors on the market. For more information visit www.aquariumeng.com.