Refactometer, what to trust?

[MarcosTacos]

I have bought this calibration solution for my refactometer, which was never calibrated (by me at least) before.
I use red sea blue bucket, which I mix using half a cup per gallon in my 5 gallon buckets. It read arount 1.025-1.026 before with the method I just mentionned.

I then got the calibration solution and it read close to 1.030 with it (I let it sit in my tank for a while before testing it).
I then adjusted the refactometer, which read 1.021 (to my fresh mix).

I also noticed the line is not at 0 with RODI water ever since I calibrated it, but it was there before.

What should I do? Calibrate with RODI water or trust the solution?

 

[Sump Crab]

I like to have several different methods to all kind of confirm each other. I have refractometer calibrated with calibration fluid, tropic marin glass hydrometer, and swing arm hydrometer. I use them to all check each other. It’s the only way I can really trust the results.

If it were me in your position I would buy a tropic marin glass hydrometer to test against.

 

[gbroadbridge]

I have bought this calibration solution for my refactometer, which was never calibrated (by me at least) before.
I use red sea blue bucket, which I mix using half a cup per gallon in my 5 gallon buckets. It read arount 1.025-1.026 before with the method I just mentionned.

I then got the calibration solution and it read close to 1.030 with it (I let it sit in my tank for a while before testing it).
I then adjusted the refactometer, which read 1.021 (to my fresh mix).

I also noticed the line is not at 0 with RODI water ever since I calibrated it, but it was there before.

What should I do? Calibrate with RODI water or trust the solution?

Many purchased calibration solutions are incorrect for varius reasons.

Best bet is to make your own.
It is very simple if you have access to an accurate scale and some table salt from the kitchen.

Simply dissolve 3.65grams of table salt into 96.45 grams of RODI water.
This will give you a solution that is 35ppt/psu and you can make gallons of it for a few cents.

Use this to calibrate your refractometer.

For detail you can refer to this article.

https://reefkeeping.com/issues/2004-06/rhf/index.php

 

[zoomonster]

If you're using a regular refractometer they tell you to never calibrate to 0 but rather to 35ppt solution (not the apex stuff either). I use the Pinpoint 35ppt/1.026sg solution.

 

[MarcosTacos]

I like to have several different methods to all kind of confirm each other. I have refractometer calibrated with calibration fluid, tropic marin glass hydrometer, and swing arm hydrometer. I use them to all check each other. It’s the only way I can really trust the results.

If it were me in your position I would buy a tropic marin glass hydrometer to test against.

If you're using a regular refractometer they tell you to never calibrate to 0 but rather to 35ppt solution (not the apex stuff either). I use the Pinpoint 35ppt/1.026sg solution.

I'm very suspicious of the calibration solution I got, as I had a second refactometer (which I sold a while back) which was also reading my salt mix correctly at 1.025-1.026 before I calibrated the current refactometer.

 

[Dburr1014]

I have bought this calibration solution for my refactometer, which was never calibrated (by me at least) before.
I use red sea blue bucket, which I mix using half a cup per gallon in my 5 gallon buckets. It read arount 1.025-1.026 before with the method I just mentionned.

I then got the calibration solution and it read close to 1.030 with it (I let it sit in my tank for a while before testing it).
I then adjusted the refactometer, which read 1.021 (to my fresh mix).

I also noticed the line is not at 0 with RODI water ever since I calibrated it, but it was there before.

What should I do? Calibrate with RODI water or trust the solution?

As said, never calibrate to rodi. The reason being, everything is not perfect no matter how much engineering they put into something. The slope could be off on your refractometer and you would never know it. So by calibrating to rodi, if you're slope is off it would be way off at 1.026. But if you calibrated to something closer to 1.026, it would inherently be closer to the newly mixed water.

 

[Budman93]

I like to have several different methods to all kind of confirm each other. I have refractometer calibrated with calibration fluid, tropic marin glass hydrometer, and swing arm hydrometer. I use them to all check each other. It’s the only way I can really trust the results.

If it were me in your position I would buy a tropic marin glass hydrometer to test against.

Yeah this is a good suggestion. Even just a cheap swingarm is better than nothing to know if you are in the ballpark of accurate readings.

 

[IPT]

Yeah this is a good suggestion. Even just a cheap swingarm is better than nothing to know if you are in the ballpark of accurate readings.

I'm no expert, but from what I recall Swingarms are not reliable at all. I could be wrong.

I think I would try the homemade solution and see where that comes in. I for one would not trust the instructions on the bucket. Maybe, if you did it by weight, but not by mixing volume. I'm going to actually try the self made solution listed above and see where mine comes in.

 

[dedragon]

I use red sea blue bucket, which I mix using half a cup per gallon in my 5 gallon buckets. It read arount 1.025-1.026 before with the method I just mentionned.

Unless you are filling up the bucket to the rim, the bucket will actually hold closer to 4 gallons and not 5. It is also just an estimate and I wouldnt use that for calibration purposes

 

[MarcosTacos]

Unless you are filling up the bucket to the rim, the bucket will actually hold closer to 4 gallons and not 5. It is also just an estimate and I wouldnt use that for calibration purposes

If that were the case, my salinity would be even higher since I add more salt than needed for the water volume I have.

 

[fodsod]

Sub'd for more info on this as I may need to find a more reliable method/procedure for checking salinity.

 

[Zach W]

Many purchased calibration solutions are incorrect for varius reasons.

Best bet is to make your own.
It is very simple if you have access to an accurate scale and some table salt from the kitchen.

Simply dissolve 3.65grams of table salt into 96.45 grams of RODI water.
This will give you a solution that is 35ppt/psu and you can make gallons of it for a few cents.

Use this to calibrate your refractometer.

For detail you can refer to this article.

https://reefkeeping.com/issues/2004-06/rhf/index.php

OP This is the easiest answer. Make the calibration solution yourself and compare against that. This calibration solution is meant only for refractometers. If you look further into the linked article it will tell you how to make calibration solutions for other methods of determining salinity as well

 

[MarcosTacos]

OP This is the easiest answer. Make the calibration solution yourself and compare against that. This calibration solution is meant only for refractometers. If you look further into the linked article it will tell you how to make calibration solutions for other methods of determining salinity as well

I unfortunately don't have a scale to measure the quantities accurately at the moment.

 

[Budman93]

I'm no expert, but from what I recall Swingarms are not reliable at all. I could be wrong.

I think I would try the homemade solution and see where that comes in. I for one would not trust the instructions on the bucket. Maybe, if you did it by weight, but not by mixing volume. I'm going to actually try the self made solution listed above and see where mine comes in.

I mean I agree but if you are worried your refractometer is off drastically at least comparing it to something else that gives you a similar reading should reassure you a little. My problem with the swingarms is that it is hard to get a proper reading since tiny bubble always stick to the arm and pull it up higher than it should be.

 

[Hatuey]

As said, never calibrate to rodi. The reason being, everything is not perfect no matter how much engineering they put into something. The slope could be off on your refractometer and you would never know it. So by calibrating to rodi, if you're slope is off it would be way off at 1.026. But if you calibrated to something closer to 1.026, it would inherently be closer to the newly mixed water.

Hope I can ask a question related to the post: However I made the DIY calibration solution calibrated, and I'm questioning my salinity in my 15 Gallon that I'm cycling. I keep measuring 1.027 regardless if I measure before or after I top off. Not sure if that's expected. In addition, I tried measuring the rodi and it appears that it falls below 0. Again not sure if this is expected or if I should go to the lfs.

Apologies if I went off thread, however thought this would be relatable.

 

[Dburr1014]

Hope I can ask a question related to the post: However I made the DIY calibration solution calibrated, and I'm questioning my salinity in my 15 Gallon that I'm cycling. I keep measuring 1.027 regardless if I measure before or after I top off. Not sure if that's expected. In addition, I tried measuring the rodi and it appears that it falls below 0. Again not sure if this is expected or if I should go to the lfs.

Apologies if I went off thread, however thought this would be relatable.

What is the question?
What size water volume?
Assuming you used the right fluid in RHF paper...
If it stays at 1.027 all the time, try adding a little more rodi to your sample. It should change.
Recalibrate to the solution and test the tank water again.

If your volume is large enough, you may not see a change with topoff. My system for instance, tunze topoff only adds a 1/4 cup when it kicks on top a 100 gallon system. I won't see a difference in SG that amount.

 

[Salty_Northerner]

Honestly $13 dollars is to much for the fluid.

Go to a shop that make their own distilled water and zero the refactometer using the said water.

Buying off the shelf Distilled store water you'll never know how pure it is.

 

[Koty]

TM glass hydrometer fragile a bit anoying but the only one I trust

 

[Court_Appointed_Hypeman]

I'm very suspicious of the calibration solution I got, as I had a second refactometer (which I sold a while back) which was also reading my salt mix correctly at 1.025-1.026 before I calibrated the current refactometer.

I calibrate mine before every use. And will have sudden drifts sometimes. But my salt as per instruction also only mixes to 1.021

 

[Dburr1014]

Honestly $13 dollars is to much for the fluid.

Go to a shop that make their own distilled water and zero the refactometer using the said water.

Buying off the shelf Distilled store water you'll never know how pure it is.

Using distilled water is the wrong way to calibrate.
I covered this in post #6. ^^^^^^^