How often are you calibrating your Hanna salinity tester? I ask because about 6 months ago I ungraded from a good quality refractometer to Tyne Hanna electronic salinity tester for a greater accuracy. I understand that the device has a +/- 1 ppt accuracy but I feel the need to calibrate at least every 3-4 weeks with a use of 4-8 times a month. My aquarium has a flawless ato and I feel it maintains a stable salinity and when I do my 10% weekly water change in the same bucket using the same measured amount of salt, but even with all my consistency the Hanna is definitely no more accurate then the +/-1 ppt. Should I not worry about this reasonably small variation or invest in a better salinity tester?