PH-Balance Marine Aquarium BufferThe pH of seawater in the open ocean is stable, normally between 8, 0 and 8, 3due to the carbonate-bicarbonate buffering system, In tide pools and aquariums the pH can vary more widely due to the influence of respiration and photosynthesis in the restricted bodies of water, In an aquarium with no illumination it is normal for the pH to drop temporarily due to respiration of CO2 in the absence of photsynthesis, 1 Kilo 2, 2 lb, SKU: RYLHC6457