Salinity Check Sanity Check

Old Dog · Jan 17, 2021

Preface this with "I'm still learning". About 7 months into the hobby now.

I buy my saltwater from the LFS. I read a post here related to good husbandry and not taking the LFS word the salinity is correct. I started doing my own checks with refractometer and found their salinity high. The next time, I added RO to get their salinity to 1.025 when doing a water change. The next time I took my water into the LFS for checks, the told me salinity was way too low at 1.022. I told them my problem. The next at the LFS, I took my refractometer and they calibrated it. I didn't see what they used. I ordered my own calibration solution. When it came in, did a check and found their calibration of the refractometer didn't match the solution. So, I calibrated and added RO water accordingly. The next time in the LFS, same thing, you're salinity is too low. At that point, I took my refractometer and the calibration solution in. The owner had to hunt for their calibration solution. The employees had been using RO water set to 1.000. He was going to order a different brand of solution to be able to double check. In the end, he told me my solution was bad and set my refractometer to his solution. I order another solution. While the two brands I purchased were not identical readings, they were very very close.

The next time I was in the LFS, they had an electronic salinity tester (not Hanna). I'm guessing my exercise with them caused that. Using it, they told me my water was 1.023. I decided to buy a Hanna electronic salinity tester. I've been very happy with the Hanna products I have. It came in with the satchets of calibration solution. I calibrated it. My aquarium was at 1.026. I added some RO. Not knowing how they calibrate their electronic tester, and that the Hanna and the refractometer are giving me the same readings, I'm saying they have something wrong. I had 10 gallon of saltwater from them I bought last weekend and 10 gallon I just bought yesterday. This morning, I used the Hanna tester on both of them. The one from last week is at 1.027 and the one from yesterday is 1.029. I'm saying their measurements are not right and will be adding RO with this water change.

Am I doing something wrong or missing something?

Thanks!

Rmckoy · Jan 17, 2021

It’s best to test your own . And as long as it’s consistent , a little higher or lower ,
Stability is the main goal .

from the business view .
it doesn’t make much sense to mix their water higher in salt .
most lfs mix closer to the 1.021

1.026 is ideal reef salinity ( 35ppt )

brmreefer · Jan 17, 2021

Not sure if all ICP tests provide salinity, but some do. Just something to consider later down the road if one is done on the system and at the same time validate your tests.

I would not do an ICP for the sole purpose of a salinity check, but running a check on the system every 6 months or year to see where parameters are at doesn't hurt.

I agree with Rmckoy that "Stability" should be the goal.

Randy Holmes-Farley · Jan 18, 2021

Old Dog said:
Preface this with "I'm still learning". About 7 months into the hobby now.

I buy my saltwater from the LFS. I read a post here related to good husbandry and not taking the LFS word the salinity is correct. I started doing my own checks with refractometer and found their salinity high. The next time, I added RO to get their salinity to 1.025 when doing a water change. The next time I took my water into the LFS for checks, the told me salinity was way too low at 1.022. I told them my problem. The next at the LFS, I took my refractometer and they calibrated it. I didn't see what they used. I ordered my own calibration solution. When it came in, did a check and found their calibration of the refractometer didn't match the solution. So, I calibrated and added RO water accordingly. The next time in the LFS, same thing, you're salinity is too low. At that point, I took my refractometer and the calibration solution in. The owner had to hunt for their calibration solution. The employees had been using RO water set to 1.000. He was going to order a different brand of solution to be able to double check. In the end, he told me my solution was bad and set my refractometer to his solution. I order another solution. While the two brands I purchased were not identical readings, they were very very close.

The next time I was in the LFS, they had an electronic salinity tester (not Hanna). I'm guessing my exercise with them caused that. Using it, they told me my water was 1.023. I decided to buy a Hanna electronic salinity tester. I've been very happy with the Hanna products I have. It came in with the satchets of calibration solution. I calibrated it. My aquarium was at 1.026. I added some RO. Not knowing how they calibrate their electronic tester, and that the Hanna and the refractometer are giving me the same readings, I'm saying they have something wrong. I had 10 gallon of saltwater from them I bought last weekend and 10 gallon I just bought yesterday. This morning, I used the Hanna tester on both of them. The one from last week is at 1.027 and the one from yesterday is 1.029. I'm saying their measurements are not right and will be adding RO with this water change.

Am I doing something wrong or missing something?

Thanks!

Don't rely on an LFS to get things right.

I'm not certain they are wrong, but there's no reason to assume they are right.

vetteguy53081 · Jan 18, 2021

I have two testers plus apex. I use the two to assure they are in agreement rather than all over the place

Old Dog · Jan 20, 2021

Thank you all for the replies. stability is my goal.

Reef. · Jan 20, 2021

You will now have realised it’s not easy to get the correct salinity.

Refractometers can be off, you need to calibrate with 35ppt that you know is exactly correct.

Calibration fluid can be off, two different bottles can read differently, especially an old bottle that has been opened many times and evaporation has changed the salinity that was already most likely incorrect from the start.

make your own, use 0.01g scales ($20 Amazon) 3.65g table salt, 96.35g rodi water.

If you want a salinity checker that is never off and never needs calibrating then buy a Tropic Marin hydrometer.