Originally Posted by Vpotts28
Well I bought a 200g bucket of Oceanic because I ran out of IO. I did a 20% WC with the new salt yesterday. I checked my calcium levels in my DT before and after the wc. I also tested the water that was going in. Before with the IO, the change water was a 440 ppm calcium, after the wc the calcium level would be near 400 ppm. After a two week period when I do my wc's my levels would be at 330ppm. My tank was at 330ppm yesterday. My levels on my change water using Oceanic was 500 ppm, after the wc they were at 485 ppm. I can't believe that, I am dumbfounded. The alkalinity was at 15 dKH.
I am dumbfounded too
a)Am I understanding your numbers correctly? your tank was at calcium of only 330ppm before the water change. you did a 20% water change with oceanic that had a calcium level of 500ppm. After the water change calcium went all the way up to 485ppm? How is possible for calcium to go up 47% overall when 80% of the old water is still there and the new mix water itself was only 51% greater in calcium than the old water. In other words 80% volume @ 330ppm + 20% volume @ 500ppm will not give you a calcium of level of 485ppm even if had a depleted magnesium level that will inhibits Ca (unlikely if you are doing regular water changes)
b)From what I've gathered its almost certain that a dKH of 15 along with a calcium of 485 ppm would cause obvious calcium precipitation within the water. From what I've read even with much more conservative numbers (calicum over 440ppm along with a dKH of over 10) it is likely to be a false alk reading because precipitation should occur.