That's why I'm going back to TM CarboCalcium instead of All for Reef, too many swings in traces for a larger system. What are using to check salinity? I'm not a big fan of digital refractometers, as some calibrate to zero using RO, which is a big no, no. TM glass hydrometer is usually spot on and it's pretty hard to mess up, as long as you're close to 77 degrees, give or take a little.