Calcium is another important chemical parameter that needs to be monitored for the long term success of your saltwater reef aquarium. It is needed by corals, invertebrates such as clams, snails, crabs, etc and even by some calcerous algae for the building of their calcium carbonate structures. These will ensure that these organisms can grow healthily. The optimum level for calcium in the saltwater reef aquarium is between 375 ppm to 475 ppm. When using additives to increase the calcium level in your saltwater reef aquarium, it is important that you also check the water pH value to prevent an increase in the alkalinity level. For more information and guide on the optimum calcium level and how to control it, click on the link.