Rising calcium level
 

Over the last month my calcium level has slowly risen from 420ppm (NSW) to 480ppm. Although not really concerned yet, I'm wondering what is causing it. Other parameters are pretty good. pH 8.3, S.G. 1.025, 10 dKH, mg 1140ppm, nitrate & phosphate no trace on test kits (Salifert & API). 20% W/C every 2 weeks. I've used I/O salt from day 1. Could it be a pail of salt? Any ideas?

Are you supplementing anything? Have you tested the new SW before adding to tank?

As for IO, tested a few pails and find all low in Ca (relative to NSW).

very small dose per week of Reef Plus Amino Acids
Tech M magnesium (small dose weekly) as mg level was a little low

I just tested the SW and CA is low