Over the last 4-5 weeks I've been settling my calcium reactor in and tuning the drip and bubble rates. I've had Kh swinging from 8-12 although its settled down nicely to 9.0, with calcium at 440.
I went overseas for a week when things hadn't settled down and Kh was 12 when i got back. During this time calcium (I presume) precipitated out onto my pumps, rocks, bottom glass, etc. made a bit of a mess as it wasn't a nice white, but a tan/brown colour, but definitely a gritty sandy solid. Also lost a couple of acros at this stage with STN, but may be more to the fluctuations than the high Kh.
Now that its settled down, definitely some growth starting to show (rapid growth on Montis) and finally getting coraline growth, although again, it doeslike the precipitate that formed.