Aquarium Systems Test Kit A new range of test kits from Aquarium Systems that accurately test your marine aquarium water. Seatest\'s calcium test kit comprises approx. 40 individual tests for calcium (Ca) levels within the aquarium. Calcium is used by many corals and invertebrates to grow shell and structure, and levels can therefore become too low over time to allow growth to continue, or will cause irregular growth patterns. Ideal calcium levels are typically 400 to 500 mg/litre. Please note this product is short dated - BBE August 2015.