Aquarium pH Buffer replenishes the carbonate and bicarbonate required to maintain or increase the alkalinity of captive marine systems. Alkalinity (carbonate hardness) in captive marine systems constantly decreases as biological processes remove carbonate, and produce acids that neutralize carbonate. Proper alkalinity should be maintained around 2.5-2.9 me (7-8 dKH) for marine fish tanks and 3.2-3.6 me (9-10 dKH) for reef tanks. We carry several products from Brightwell Aquatics, Seachem, Fauna Marin, and Two Little Fishies (C-Balance) that will help you maintain your pH. Related Article:Why is My Aquarium pH so High/Low? How To Achieve the Proper Aquarium pH