All my kits are new. I test so much, I am constantly buying new kits or reagent refills.
On the Hanna calcium I used to use my own RO/DI until I read that the kit tests better with Hanna's deionized water but the results are nearly identical for me.
Here is what really throws me off.
I'll test my tank calcium with Hanna at 436 and Salifert at 365, so I'd assume there is a difference of 71. Then I'll use those very same kits and test my salt reservoir and Hanna reports 441 with Salifert at 440, nearly identical. I double-check the results and re-test and it's nearly identical on both.
When I use Red Sea's MyBatch on my Coral Salt Pro, they report Magnesium at 1388, calcium at 451, and alkalinity at 11.9. Salifert calcium is 435, Hanna calcium is 504, Salifert magnesium is 1440, and Hanna alkalinity is 10.6. At that point my reservoir was three days old. At fifteen days old Hanna alkalinity is 10.4, Salifert calcium 440, Hanna calcium 441, and Salifert magnesium at 1290.
Point is, on day three of my reservoir, there was a big difference between Salifert and Hanna calcium but on day fifteen they were nearly identical.
Perhaps I'm digging into this too much.
Quote:
Originally Posted by bertoni
The Red Sea and Salifert kits agree reasonably well, and I'd probably trust them. The Hanna calcium meter is known to be a bit more problematic because of the dilution, so I think it's close enough. The Red Sea and Salifert magnesium resultts disagree a fair amount. Is one kit getting older? Kits will be less accurate as they get older because water evaporates from the reagents over time.
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