Thank you, @Deanna
, this is the hard-hitting analysis I came to this thread for!
Now I have new questions:
1. It seems like all my other metal-sulfates were added in such small quantities that there wouldn't be enough free SO4 for all this Ca. Wrong? I haven't done actual chemistry braining in a lot of years.
2. What happens to the other metals now that Ca has stolen their SO4?
3. (or 2B) Is this bad? Can I just ignore the precipitated CaSO4 and move along?
Without doing the math, it’s hard to say - correctly - at what point there will be enough SO4 to combine with Ca to cause precipitation. It is, obviously, happening. By conducting the test I mentioned, you can see where the cutoff roughly exists.
Once the ions dissociate, the plants will, hopefully, consume them before they can oxidize. This is why we dose small quantities frequently (usually daily) of the DIY mixes, which are not chelated. If they were chelated, we wouldn’t have these concerns.
Since you are getting the Ca and SO4 elsewhere, then you can ignore the CaSO4 that has precipitated. If you are using a doser, it may accumulate and clog the line. If it is put into the tank, it will dissolve.
I also see that I may have misled on the Cl issue. When the CaCl dissolves the Cl2 actually dissociates into the two chloride ions and does not remain as elemental chlorine.