HR Nitrate Remover? is designed for aquariums that have higher than 15ppm nitrate. It is formulated specifically to reduce high nitrate within marine/reef environments and works by providing bioavailable carbon sources to denitrifying bacteria present in media, deep sand beds & inner pores of live rock. The bacteria oxidise the carbon into carbon dioxide while reducing nitrate to chemically inert nitrogen gas. If you are experiencing nitrate 15ppm or lower, we recommend using our LR Nitrate Remover?.