Does calibration fluid for refractometers go bad?

[stanleo]

Decided to test my calibration on my refractometer cause I haven't done it in a while. Tank is doing great and my salinity has been spot on for months but just decided to do it and it is WAY off. With the fluid it reads 46ppt. If I corrected it the salinity of my tank would be 26 ppt. Nothing is struggling in the tank. Hard and soft corals are growing well and the fish and inverts are all happy. Does the fluid go bad? I have had it for over a year and only used it a couple times before this. Left it out in the open in my fish room. I have an ATO that I haven't had issues with and the water in there is reading 0 TDS.

I tried calibrating with RO water and it is off slightly but not to this extent. And I did shake the bottle before using and read the directions to be sure I was doing it right. What is going on here?

 

[Red_Beard]

If any of the solition evaporated then it would be off and read too high. If the bottle was 100% air tight and the lid was on all the time and not left open, it should be good still. But, plastic is permeable and no lid is guaranteed 100% sealed. Id get another bottle if it were me. Everything seems happy, it will probably stay happy for another 5 days while it ships(unless the lfs has some). Plus they are only $5. Other thing to make sure is that your refractometer isnt toast, have a buddy or lfs double check your reading if possible. If you are still super concerned something is amiss, the tropic marin precision hydrometer would be a good solid baseline.

 

[stanleo]

If any of the solition evaporated then it would be off and read too high. If the bottle was 100% air tight and the lid was on all the time and not left open, it should be good still. But, plastic is permeable and no lid is guaranteed 100% sealed. Id get another bottle if it were me. Everything seems happy, it will probably stay happy for another 5 days while it ships(unless the lfs has some). Plus they are only $5. Other thing to make sure is that your refractometer isnt toast, have a buddy or lfs double check your reading if possible. If you are still super concerned something is amiss, the tropic marin precision hydrometer would be a good solid baseline.

Now that you say that, the cap was twisted open when I got it out. I will get another bottle, thank you.