Win a Hanna Instruments Calcium Checker Colorimeter! Calcium is an essential building block for corals, clams and coralline algae. This week we are giving away a Hanna Instruments Calcium Checker Colorimeter (a $49.99 value!) so you can easily and accurately measure the calcium level in your reef tank. Tired of using complicated chemical test kits? ENTER NOW. Registration ENDS at 11:59 PM PST on 12/20/13. Details: Open to US residents 18 years or older. Void where prohibited or restriced by law. Winner will be contacted via email.