Most ocean acidification (OA) experimental systems rely on pH as an indirect way to control CO2. However. accurate pH measurements are difficult to obtain and shifts in temperature and/or salinity alter the relationship between pH and pCO2. Here we describe a system in which the target pCO2 is controlled via direct analysis of pCO2 in seawater. https://poolsproductscanadas.shop/product-category/hayward-xstream-parts/