It should either come with a test sample or do the calibration with distilled water.
You should trust the refractometer vs
hydrometer. I had 2 swing arm hydrometers and both were registering .003 - .004 less than my refractometer. Needless to say I was running a 1.0295 SG
. All my corals and livestock were just fine, although they do look better now with a SG
of 1.026. It took me a whole month to bring it down.
Be very careful lowering your SG
to where you want it. Rapid changes in salinity stress out corals, fish, and especially invertebrates.
29gal BB | 42+ lbs LR
| 143watts PC
| Asst. Leathers, Frogspawn, Hammer, XLG Open Brain, Zoanthids, Mushrooms, Diploastrea heliopora | Blue Mandarin | Atrosalarias Fuscus | Pair Captive Bred Ocellaris Clowns | Peppermint Shrimp | 6 Astrea's |