I'm pretty sure this hasn't happened overnight. I don't have anything that is a huge calcium pig.
The API test consistently returned results around 500. I figured it was my salt, as even newly mixed water tested high. I even spoke to Kevin at Red Coral about it, but as my test was new and not expired it never occurred to anyone that the results would be horrifically out (maybe a bit, but not by 200ppm!). We figured it was probably as result of not rolling my salt bucket well enough.
I stopped doing water changes in an attempt to let the calcium fall naturally, and I started dosing trace elements and a few other things. The calcium never fell. Now, I'm a pretty smart woman (despite looking like a dumb @$$ right now), and It still never occurred to me at my test was faulty (I'm in engineering, but I'm no chemist
).
The new Seachem Calcium test is bang on (based on testing it against reference solution). I wish I still had some of the API test left so I could test that against the reference solution. It would probably indicate that the reference solution was 700.
Two of my SPS are growing nicely, despite my huge blunder.
I'm going to throw out every API test I have.