Seachem Laboratories - Aqua Vitro Reef. Eight. four supplies a properly balanced (carbonate/bicarbonate) buffer system that yields an industry leading pK of 8. 6 which makes pH maintenance of 8. 3-8. 5 easy. A higher pK increases the buffer's ability to counteract inevitable acidic sources in the water. eight. four will safely raise marine pH while adjusting alkalinity. eight. four contains a concentrated, balanced blend of bicarbonate and carbonate salts designed to restore disrupted buffer systems and increase carbonate alkalinity. 11.8 oz