Maintaining stable parameters in the accepted range is much better than chasing “ideal” numbers

Question:  I’m having an issue with the calcium and alkalinity levels in my reef tank. Right now, the calcium is at 380ppm, which is at the low end of the acceptable range, and the alkalinity is at 10dKH, closer to the high end of the acceptable range. I’d like to get the calcium up over 400ppm so I have a greater margin for error. But whenever I add more calcium supplement than usual, I notice that the alkalinity level drops afterward. Any idea why this is happening? Is it coincidence or cause-and-effect?” – Submitted by Ross C.

Answer: Thanks for your question, Ross!  The drop in your alkalinity level subsequent to increased calcium supplementation is likely cause-and-effect rather than coincidence, and the reason for this is fairly easy to understand—even for a right-brained hobbyist like me.

You see, any given volume of water can hold only so much in the way of dissolved solids. If your aquarium water is already holding all the calcium and buffering compounds it can, adding more of one will tend to displace some of the other. Thus you can get a seesaw relationship between the two levels if you don’t dose them in a balanced fashion.  MORE