Since there is still market shrimp, it could take a while for the bacteria in the sump to remove the ammonia. Hence it could be at 0.5. Nitrate removing bacteria is harder to maintain as they require low level oxygen levels to thrive. If u r using good media, there might be enuff of such denitrifying bacteria to reduce nitrates to 0. If nt carbon dosing will help Sent from Singapore Reef Club mobile app