I have been using a Deep Six swing arm hydrometer for a long time. I followed all of the recommendations and rinsed it after every use and even soaked it in vinegar once every month or two. I recently bit the bullet and bought a refractometer and was shocked at what I found.
My hydrometer (purchased new about 6-8 months ago) was reading 1.026 but the refractometer informed me that I was really at 1.31 (40 PPT). I checked the calibration on the refractometer several times because I couldn't believe it was that far off but it was. I have lost a couple of SPS corals and 2 margarita snails over the last couple of months and never could figure out why. I think high salinity might be part of the problem I was having.
I have since lowered the salinity (SLOWLY) and things are doing well. I just wanted to post this to let people know that if you have a swing arm hydrometer, have it checked against a refractometer to see if it's accurate. If it's not, then at least you will know and you can adjust your system accordingly.
My hydrometer (purchased new about 6-8 months ago) was reading 1.026 but the refractometer informed me that I was really at 1.31 (40 PPT). I checked the calibration on the refractometer several times because I couldn't believe it was that far off but it was. I have lost a couple of SPS corals and 2 margarita snails over the last couple of months and never could figure out why. I think high salinity might be part of the problem I was having.
I have since lowered the salinity (SLOWLY) and things are doing well. I just wanted to post this to let people know that if you have a swing arm hydrometer, have it checked against a refractometer to see if it's accurate. If it's not, then at least you will know and you can adjust your system accordingly.