Sulfur denitrator increasing CA?

[pixelhustler]

I use a Neptune DOS for 2-part dosing, but ever since I added a sulfur denitrator I had to stop dosing calcium. My Trident has been reading calcium at 600-640 consistently with very little variation between tests. On the other hand, alkalinity has decreased substantially and I had to increase dosing by 30%.

The sulfur denitrator has sulfur media at the bottom and aragonite + crushed coral at the top. Could this be replenishing calcium the same way a calcium reactor does?

 

[Dennis Cartier]

It may seem like it is boosting calcium, but that is only because it is depleting alkalinity. Which causes calcium to rise when you are dosing 2 part in equal proportions.

When nitrate is created, some alkalinity is utilized and lowers the alkalinity level as a result. When the nitrate gets used, the alkalinity gets returned, raising the alkalinity level by the equal amount it was lowered by initially. However, in the case of sulfur denitrification, the alkalinity is not returned as it gets consumed as part of the process. The end result is an imbalance in calcium and alkalinity and the need to provide extra alkalinity to offset the alkalinity lost during the denitrification.

The aragonite and crushed coral will be acting to buffer the efflulent inside reactor to try and keep the pH from being too low when it is returned to the tank. Any calcium that is released, will be accompanied by an equal amount of alkalinity being created during the process, just like in a calcium reactor, which provides both calcium and alkalinity.