Bulk Pharma Soda Ash 7 Pounds Bulk Reef Supply LDK Wet cycled live rock or Size:139gal 36"x30"x30" Internal Overflow Clear Background Wet cycled live rock or even previously cycled wet man made rock will work fine (although this may be a bad idea due to the possibility of introducing parasites or pathogens from another aquarium) General Calcium Adjustments Create a 1 gallon solution by following the Mixing Instructions above and then test your aquariums current calcium level and using the BRS Reef Calculator input your current and desired calcium levels along with your total system water volume The difference between the starting point and the final reading is how much alkalinity will need to be replaced over the course of a 5 day span of time Remove the cap and fill the container the rest of the way with RO DI or distilled water