Which salinity reading?

[Nemoreef]

Setting up auto water changer and mixed the bin. I wanted my salinity to be accurate so measured with

Hanna at 32.8ppm[aiming 35ppm]
BRS refractometer at 35
TM Hydrometer at 1.0275[35ppt equivalent is at 1.026?]

All measured at same temperature around 68°F and same time. Which one to trust? I calibrated hanna and refractometer right before testing. Refractometer says ATC on it so I am assuming it is temperature corrected? What am I doing wrong here?

I also saw one post from 2018 by Randy, it was actually a question to what salinity will a 35PPT at 20C change when checked at 30C. If this is the case, what salinity are we supposed to mix the bin to, if it's going to change when it reaches tank temp?

 

[slingfox]

I originally had a Hanna checker and cheap (ie, $34.99 from PremiumAquatics.com) refractometer. I could not get them to read consistently and assumed the refractometer was right. I eventually got tired of the inconsistency and got a high end Vee Gee refractometer off Amazon. The Vee Gee showed that the cheap refractometer was way off (read consistently higher than true salinity) and the Hanna was pretty much inline post-calibration. I should have got the Vee Gee from the start!

 

[Nemoreef]

I originally had a Hanna checker and cheap (ie, $34.99 from PremiumAquatics.com) refractometer. I could not get them to read consistently and assumed the refractometer was right. I eventually got tired of the inconsistency and got a high end Vee Gee refractometer off Amazon. The Vee Gee showed that the cheap refractometer was way off (read consistently higher than true salinity) and the Hanna was pretty much inline post-calibration. I should have got the Vee Gee from the start!

I wish the same now, all three devices together and I could have bought Vee gee. In my case, I don't trust my Hanna, I calibrated to 35ppt solution and I waited a few mins and measured the same solution again and it read 34.6ppt.

 

[QuickrdenU]

I wish the same now, all three devices together and I could have bought Vee gee. In my case, I don't trust my Hanna, I calibrated to 35ppt solution and I waited a few mins and measured the same solution again and it read 34.6ppt.

If you have testing solution that you know is 35 and you calibrate and test, even a cheap refractometer should be accurate I would think. I went through this same process with 5 different devices. They’re all off by a point or 2. I chose to rely on my refractometer ultimately. I just make sure to calibrate often to compensate for temperature changes.

 

[vetteguy53081]

Setting up auto water changer and mixed the bin. I wanted my salinity to be accurate so measured with

Hanna at 32.8ppm[aiming 35ppm]
BRS refractometer at 35
TM Hydrometer at 1.0275[35ppt equivalent is at 1.026?]

All measured at same temperature around 68°F and same time. Which one to trust? I calibrated hanna and refractometer right before testing. Refractometer says ATC on it so I am assuming it is temperature corrected? What am I doing wrong here?

I also saw one post from 2018 by Randy, it was actually a question to what salinity will a 35PPT at 20C change when checked at 30C. If this is the case, what salinity are we supposed to mix the bin to, if it's going to change when it reaches tank temp?

1.026 is reef aquarium standard

 

[Nemoreef]

If you have testing solution that you know is 35 and you calibrate and test, even a cheap refractometer should be accurate I would think. I went through this same process with 5 different devices. They’re all off by a point or 2. I chose to rely on my refractometer ultimately. I just make sure to calibrate often to compensate for temperature changes.

I would think that's the case but how can they give such different readings? I might be OK with the Hydrometer reading as it is calibrated to read at 25°C and my water is at 20°C. But the difference in a calibrated Hanna and refractometer doesn't make any sense. Unless my the calibration solution for hanna is off.

 

[Nemoreef]

1.026 is reef aquarium standard

That's the goal but since there is temperature variation, do we have to mix the solution at tank temperature[in my case 78°F]? How do we correct for that? I am not planning to heat the mixing bin.

 

[vetteguy53081]

That's the goal but since there is temperature variation, do we have to mix the solution at tank temperature[in my case 78°F]? How do we correct for that? I am not planning to heat the mixing bin.

You don’t have to but assure your salinity tester is calibrated and accurate

 

[Gtinnel]

I have the Hanna salinity reader and I have never been able to get an accurate reading from it. I know others swear by them but mine has never given a consistent reading.

 

[Nemoreef]

I have the Hanna salinity reader and I have never been able to get an accurate reading from it. I know others swear by them but mine has never given a consistent reading.

This is my case to I believe. So how do you manage?

 

[Gtinnel]

This is my case to I believe. So how do you manage?

I have a Milwaukee digital refractometer and I trust it fully. I keep a bottle of diy solution with a known salinity and the Milwaukee always reads correctly when I check it. I also keep a cheap refractometer that can I can verify my Milwaukee with if I ever need to.

 

[BeanAnimal]

Setting up auto water changer and mixed the bin. I wanted my salinity to be accurate so measured with

Hanna at 32.8ppm[aiming 35ppm]
BRS refractometer at 35
TM Hydrometer at 1.0275[35ppt equivalent is at 1.026?]

All measured at same temperature around 68°F and same time. Which one to trust? I calibrated hanna and refractometer right before testing. Refractometer says ATC on it so I am assuming it is temperature corrected? What am I doing wrong here?

I also saw one post from 2018 by Randy, it was actually a question to what salinity will a 35PPT at 20C change when checked at 30C. If this is the case, what salinity are we supposed to mix the bin to, if it's going to change when it reaches tank temp?

The TM Hydrometer should be your reference. It is calibrated for 77F - you need to use a conversion table. DO NOT USE THE TABLE FOUND AT BRS IT IS WRONG.

 

[BeanAnimal]

I have a Milwaukee digital refractometer and I trust it fully. I keep a bottle of diy solution with a known salinity and the Milwaukee always reads correctly when I check it. I also keep a cheap refractometer that can I can verify my Milwaukee with if I ever need to.

My experience with that device (I will not call it an instrument) was terrible. I use the TM as the reference, but thought the digital refractometer would be a good day to day. It was all over the place.

 

[BeanAnimal]

https://reefkeeping.com/issues/2004-07/rhf/table1.pdf

 

[Gtinnel]

My experience with that device (I will not call it an instrument) was terrible. I use the TM as the reference, but thought the digital refractometer would be a good day to day. It was all over the place.

I know that it’s stated accuracy isn’t great but for me it has always read my validation solution correctly.
I often wonder on devices like these if there are differences in reliability from one device to the next. Like I mentioned earlier I have the Hanna conductivity pen and never get accurate or even consistent readings, but I know plenty of others who love theirs.

 

[Nemoreef]

Thank you. This is good information. I did not know that was an option.

 

[Nemoreef]

The TM Hydrometer should be your reference. It is calibrated for 77F - you need to use a conversion table. DO NOT USE THE TABLE FOUND AT BRS IT IS WRONG.

My temperature and salinity reading is just outside of that chart but at 23°C and 1.0270 it reads 34.91. So if I extrapolate a little at 20°C and 1.0275 is really close to 35 which means the refractometer and Hydrometer is a match. So hanna is off. I will check if I can quote that post here by Randy, it says the temperature change can cause a huge variation in salinity so if I have my mixing bin for AWC at 35PPt 20°C and tank at 26°C, won't it lower the overall salinity of the tank eventually?

This is the thread

Thread 'Reef Chemistry Question of the Day #264 Temperature and Refractometers' https://www.reef2reef.com/threads/r...ay-264-temperature-and-refractometers.385611/

 

[Gtinnel]

it says the temperature change can cause a huge variation in salinity

The change in temperature doesn’t actually change the salinity of the water. It just changes what our testers read the salinity as.

 

[Nemoreef]

The change in temperature doesn’t actually change the salinity of the water. It just changes what our testers read the salinity as.

Ok that makes a lot of sense now. I was just wondering how everything in my tank survived this long with low salinity.

 

[BeanAnimal]

I know that it’s stated accuracy isn’t great but for me it has always read my validation solution correctly.
I often wonder on devices like these if there are differences in reliability from one device to the next. Like I mentioned earlier I have the Hanna conductivity pen and never get accurate or even consistent readings, but I know plenty of others who love theirs.

Ohh I am sure there are QC issues.