Marine pH should be 8.2—8.4. Tanks dosed with limewater may go as high as 8.6. Natural sea water has a total alkalinity of 2—3 meq/L, but aquarium water should have a total alkalinity of 4—6 meq/L. This test kit features a unique dye that has a pronounced color change between 8.0 and 8.3, making it the easiest kit on the market to read in that critical range. It is suitable for marine or brackish water only. Alkalinity may be read from the same sample in 0.5 meq/L increments. MultiTest™ Marine pH & Alkalinity performs over 75 tests and contains a reference sample for validation. This kit measures total alkalinity. Total alkalinity is a measure of the carbonate, bicarbonate, borate and hydroxide content of the water, expressed as the acid neutralizing capacity of the water in meq/L (milliequivalents/Liter). The expression of alkalinity as meq/L is chemically sound and the most useful way to express this property of the water to resist change in pH.