My water parameters have taken a strange turn. I stopped doing water changes and think since I've started using activated carbon, my calcium and alkalinity have started falling about 20ppm (calcium) a week and my kH a little bit slower, but did fall from 9 down to 7 over the last few weeks. Is that common while running carbon? I've had to start running kalkwasser and added more magnesium to help stop the fall and bring the levels back up. I'm not very good at correcting my calcium and alkalinity as I've had little experience in doing so. I figured since I only have 2 tiny corals, not doing water changes would help bring my nitrates up a bit and would also removed unwanted nutrients that my algae were feeding on. But i didn't expect to see that much absorption of calc and alk.