Instant Ocean Reef Crystals - low ca, mg

[lost66]

I am not way off. I test water from my lfs when I am buying corals and I have the same result as they have. This is simple device and when handled with respect it will serve you well.

 

[R33FLIF3]

refratometers are simple.. i only have had to calibrate my refratometer one time about 6 years ago.. every time tested it is dead on .. if i test rodi my refractometer reads 15ppt below zero.