Red Sea Refractometer - constantly needs calibration

lyscer · Apr 13, 2015

Hey Guys,

So I wanted to get a nice refractometer so I went with the Red Sea Refractometer (Brand new) because it had great reviews on Amazon. However I am finding that it needs constant calibration. I will pull it out of its case test my water, put it back in its case (on a shelf next to the tank). I will then test the very next day and my salinity will appear to change. I wanted to see if anyone else was experiencing this.

To try and solve this mystery, here is what I tried.

1. It claims that it should be calibrated with 0 TDS water so I turn on my RO/DI out let water and let it drip directly onto the refractometer glass so that there are no chances of a dropper having residual tank water in it.
2. I then turn the screw and calibrate for 1.0 ppt since that is the bottom most line (light source is the same one to check tank water)
3. I wipe the refractometer off with a paper towel
3. I then check the tank water by aiming the refractometer at a light near the tank
4. I wipe the refractometer off with a paper towel
5. I put the refractometer back in its case

The very next day the 0 TDS test will reveal that the Salinity straight out of my RO/DI unit is 3-4 ppt. Anyone else seeing something similar or have any thoughts on what I may be doing incorrectly?

mike007 · Apr 13, 2015

I have also found that I have to recalibrate every time before using it. Hopefully someone will have a answer with this issue.

BayouCityReefer · Apr 13, 2015

At least we can recalibrate it with a screw driver and RO/Di . I only have to do it once a week, it's really not a big deal , just get use to checking it and making sure it's zero first off before using it to check the salinity. Still better than most others.

lyscer · Apr 14, 2015

So I wrote Red Sea an email asking them about this once I realized that others were having issues and they responded super quick. Here is the email chain:

Hello,
I recently purchased a brand new Red Sea Refractometer and I have found that I constantly have to recalibrate it. I have found that even in the span of 12 hours the unit will need to be recalibrated. I have followed to instructions on calibrating that are found in the manual, but I wanted to see if there were any other items that I could try to get the unit to stay calibrated for a longer duration of time that has been uncovered since the manual was created.

Any help is appreciated – or a disclaimer in the manual would be nice because I almost wiped out my tank because I was not adding enough salt to my water changes because the refractometer was changing and not staying zeroed out.

Thanks.

Red Sea Response

It is required that the refractometer is calibrated before every use.

So it is kind of sad that this is the response - but I guess it is what it is. Recalibration prior to every use it is. Looks like I will be building my arduino salinity tester sooner than I thought

Clownfishy · Apr 2, 2023

I know this is an old thread but thanks for this as I thought I was going mad! I brought one ages ago and put in a cupboard and never used it until the other day and could not understand why the following day it lost calibration. What a total waste of money these are. I have just brought the H2 Ocean one and that holds calibration perfectly so looks like the Red Sea refractometer is going back in the cupboard to gather dust!