Reef Tank Calcium Level Calculator
Calculate exactly how much calcium supplement to add to your reef tank.
Total system volume
What calcium level do reef tanks need?
Reef corals need 380-450 ppm calcium for healthy growth. Natural seawater ~420 ppm. Maintain within this range - test weekly if actively dosing, monthly if stable. Stability matters more than exact number - large swings stress corals. Adjust slowly: no more than 25 ppm per day change rate. For tanks with high demand (fast coral growth), top off and kalk solutions may be needed.
How do I raise calcium safely?
Calcium supplements: limewater (kalkwasser) raises calcium AND alkalinity (best method), two-part solutions (calcium chloride + soda ash/sodium bicarbonate separate), calcium reactors. Add at pump outlet, dose slowly (drip). Never mix supplements undiluted. Calcium in tank should test 400+ but also match alkalinity: if raising one, raise both proportionally. Avoid over-dosing.
What is the relationship between calcium and alkalinity?
Both essential for coral skeleton (calcium carbonate). Maintain ratio: for every 2 dKH alkalinity increase, add ~28 ppm calcium or add proportional when dosing. Reef Pro two-part: use equal amounts of limewater two-parts to maintain balance, then use Kalk to refill. Test both weekly during adjustment. Calcium:alkalinity ratio affects coral growth. Use test kits: titrations more accurate than strips for these parameters.
Can I use普通calcium supplements?
Never use calcium supplements designed for freshwater aquariums or swimming pools - contain additives toxic to fish and invertebrates. Use reef-specific products only. Swimming pool calcium chloride can be used but must be 100% pure and free of algaecides - this is advanced. Most reef keepers use two-part solutions from reef supply companies. Buy supplements from aquarium retailers only.