Originally Posted by fort384
has not been dropping much at all, just alk
. There has been a ton of coralline growth over the last few months, so maybe that is soaking up the excess carbonate, but it has definitely not been a linear relationship between Ca
Originally Posted by CorallineAlgae
Ah. It may be magnesium and strontium that's low. Coralline algae growth taxes strontium and magnesium hard. From what I've read coralline algae is made up of strontium but also requires magnesium, bicarbonates and calcium and when it has a burst of growth it can drop those levels.
When calcification occurs, as in hard corals growing the skeletons or coralline algae growing, there is a defined amount of elements used in this process. For every 1 meq/l (2.7 dKH
) of alkalinity used, the process also uses aprox 18ppm calcium, 1ppm magnesium and 1ppm strontium.
This is a great article on the subject...
When Do Calcium and Alkalinity Demand Not Exactly Balance? by Randy Holmes-Farley - Reefkeeping.com
"Another reason that calcium and alkalinity demand is not exactly balanced in many aquaria has to do with water changes. Many aquarists (including myself) do not attempt to match the calcium and alkalinity levels in water change water to the aquarium water. Consequently, each water change will alter these levels in the aquarium, and will alter the observed balance between calcium and alkalinity demand. What direction the change takes, however, will depend on the salt mix chosen and the aquarium water parameters. Commercial salt mixes vary from high calcium and normal alkalinity to high alkalinity and low calcium.
For example, if the aquarium is maintained at 420 ppm
calcium and 4 meq/L of alkalinity, and the water change has 500 ppm
calcium and 2.5 meq/L of alkalinity, each 20% water change will increase calcium by 16 ppm
, and will drop alkalinity by 0.3 meq/L. Using the same water change scenario used in the nitrate calculations above (10 changes of 20% each over the course of a year), these water changes will increase calcium by 160 ppm
and drop alkalinity by 3 meq/L."