I have a 75 gal mixed reef tank with fish. It has a trigger sump. My alkalinity has been pretty stable but the last 2 weeks it is slowly creeping up. All my parameters are steady except alkalinity. I do a 10-20% water change every 2 weeks. I use Red Sea Coral Pro salt. I have my automatic doser set to stop dosing if the level reaches 11. Any thoughts? The actual Salt reading is closer to 32, it had some micro bubbles.