Bad Calibration Fluid?

[sgraves2505]

I recently purchased some pinpoint salinity calibration fluid to check my refractometer. When I tested my refracto, it showed to be way off. The salinity calibration fluid was suppose to be 1.026 and it was reading 1.020. So after I calibrated the refracto, my tank is now reading 1.031. Could the calibration liquid be bad? I tried to follow the DIY thread and make my own calibration liquid, and it shows that my refracto was calibrated correctly before I adjusted it to match the pinpoint calibration liquid.

Also, when mixing water and following the instructions on the bucket, I was getting really close to the 1.025 before I adjusted my refracto.

I also purchased a cheap hydrometer swing arm, and it shows that my tank is right at 1.025, which is what my refracto was reading before i calibrated it with the fluid.

Is this calibration fluid maybe only for electronic salinity monitors?

I'm currently running my fish through hyposalinity for ich treatment, so a properly calibrated refractometer is a must.

Thanks

[Jefe12234]

The Pinpoint calibration fluid can be used for refractometers and I would trust it over anything else (as long as you haven't left the cap off long enough for it to evaporate significantly). When I first used it to calibrate my refractometer, I found it was off by about 4ppt. Also, in order to reach 35ppt (or ~1.0265) with Instant Ocean, I have to mix .6 cups per gallon as opposed to the .5 listed in the instructions.

As for hyposalinity, that's a little more tricky if you really want to be accurate. Calibrating at 35ppt with the Pinpoint fluid will make the refractometer accurate at 35ppt, but not necessarily at other values. And calibrating at 0ppt with purified water will make the refractometer accurate at 0ppt, but not necessarily other values. Since hyposalinity is usually done at around 12ppt or so, you may want to average the two calibrations. You could do this by calibrating at one value, then checking the other value and adjusting the refractometer halfway between it's current reading and where it should be. That should make it pretty accurate at the middle range. Then you would want to recalibrate with the Pinpoint fluid to test normal salinity again.

[Amphiprion]

It may be worth using a homemade calibration solution to check it. As long as you use precise and accurate means to measure the masses and volumes, it should come very close to the pinpoint solution. The last few times I made it, it was either dead on or +/- 1 ppt. I figured from that that the pinpoint solution was very close, if not slightly more accurate.

[Macimage]

I was having troubles with my new Pinpoint solution tonight. I calibrated by refractometer and it was off 4-5 ppt (too high). I adjusted it to 35 ppt and then when I did another test with the Pinpoint, it as off a few ppt the other way. I thought maybe it was my calibration screw on my refractometer.

I was looking around for an old swing arm!

Just thought I'd post my experiences that I had tonight. I will work with it again tomorrow.

Joyce

[boxfishpooalot]

I would not trust it. See my experience with it here:

http://www.reefcentral.com/forums/showthread.php?s=&threadid=1007891&highlight=pinpoint

[Macimage]

Thanks for the link! I will send the Pinpoint bottle back to Dr. F/S and go back to calibrating with RO/DI or Randy's solution.

Edit: I just checked using the Pinpoint solution and my refractomer is back up to 40 ppt after doing nothing to it overnight.

I calibrated it with RO/DI water and it was off by 1 ppt. After recalibrating to the RO/DI water, my tank is at 35. There is no way I am going to use this Pinpoint solution again!

Joyce