New Here! Calcium testing

[British_eh]

So, have the API and the Salifert
API readings 450 in tank one, 440 in another
Salifert readings 375 in tank one, 390 in another
Similar spread, which can be taken as more accurate. Had tank a year, so know a little bit. Just puzzled by the test results. Tests taken within minutes of each other, etc.
ANY ideas?

Cheers, British_eh

 

[reefman]

Salifert

 

[British_eh]

What do you think of Red Sea?