Hobbyists-Make Sure your Refractometer is Calibrated Correctly to your Reef Aquarium!

If you are using ro/di water to calibrate your refractometer, it's a possibility that your tank water may be off. Ro/di water is filtered water and whatever readings the filter puts out is what you get. You may not be accurately calibrating your refractometer if you are using this method. And we all know that inaccuracies in a reef tank, even if slight, can cause major problems with your fish and corals. Even distilled water can vary.

So what is the safe alternative? Use calibration fluid. Calibration fluid is consistent by design and tightly controlled.

One person learned this before it was too late:

"I was at my LFS and bought a bottle of pinpoint salinity monitor 53 ms calibration solution. I checked it with my refractometer and it read 1.031.... Whoa!!! so i calibrated it to this solution to read 1.026 then checked my tank water and it read 1.020... Holy toledo!!! i guess this explains why some of my SPS are looking like crapola!!!"

So to avoid any possible problems buy a $3 bottle of solution and check your refractometer with it. Especially if you have been calibrating it to read 0 using ro/di water, your meter will be off. Yes, it works in theory (in an ideal world), if the ro/di unit is very accurate in every section of the scale. However, in reality, most are not--even more expensive models.