Well as some know i have just redone my DT after a sponge infestation, so i decided to check my salinity which i do from time to time, about once a year on average. Used a friends refractometer and found my salinity down at 1021 so added salt to my top ups which in winter are about 20 - 30L per day for a few weeks. Took a reading a couple of days ago and it was 1022, damn still a long way to go. Visited another friend with a refractometer today and it gave me 1026 and i haven't added any salt in between tests. Both refractometers are new, both were calibrated at the time of the test and both these guys run their DT's at 1025 and the live stock in both are thriving. Do i now have to find a 3rd refractometer to check against.