They don't reduce nitrate production. They remove it. Or to be more accurate they are a carbon-rich medium that gets colonised by bacteria which remove it.doosty said:That's not entirely accurate. Yes, best way to limit Nitrates is frequent water changes and live plants.
However, bio-polymers like Dr. Tim's NP- Pearls will reduce Nitrate production in a reactor setup or in canister filter.
To be clear: they will reduce Nitrate production, not remove it.