Triton Labs doesn’t test your salinity, but they tested for Na, Mg, and Ca. Na alone showed my salinity to be at least 1.010 SG so it’s reasonable to assume the Mg and Ca made up the rest of the 0.015 SG I strive for considering both of those were at standard levels. Therefore, in my opinion, the refractometer is very reliable. It may not be as precise as a properly calibrated, and carefully performed, Hanna test, but those seem to be easier to calibrate incorrectly, if not done patiently, and precisely. Again, it may be worth the money for the peace of mind if it turns out not to be the issue. They sell them on Amazon with Prime delivery for $55 the last time I checked.