Temperature and it’s affect on Salinity

adamf83

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For the past 2 weeks I’ve been topping off with salt water in order to raise my salinity after I found it to be at 1.020. I’ve been testing the salinity every day, but I’m struggling to get it above 1.022, just crept up to 1.023 at one point.

I use the Hanna Salinity checker, I’ve calibrated it twice but still not getting readings that are going up in line with topping off with salt water. I’ve done some comparison with my refractometer, taking readings from various places.

DT: Hanna = 1.022 (27.9 Celsius), Refractometer = 1.026
Sump: Hanna = 1.022 (27.9 Celsius), Refractometer = 1.026
Top Off Salt Water: Hanna = 1.029 (21.5 Celsius), Refractometer = 1.031
Distilled Water: Hanna = 1.000 (21.4 Celsius), Refractometer = 1.000

I know the Hanna will compensate for temperature, but how much is temperature playing a part in my readings and could this be contributing to the issue I had with lower salinity?

I want to switch back to normal top off, but I want it to be at the right time.

The tank temp reads 27.9 Celsius
 
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Jedi1199

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Have you calibrated your refractometer? There are a few threads here on how to make your own DIY calibration solution.

From what I have read, temp should not play a role in salinity readings. Personally, I mix my SW at tank temp. I know there are many people here who mix theirs cold. Perhaps they can offer something to help with that specific issue.

I don't know if the Hanna checker can be calibrated or not. If it can, I would suggest that you calibrate them both and then see where that gets you.

As for raising your salinity, I believe you are doing it the right way. Better to go slowly with that as to avoid stress on your stock.
 

Randy Holmes-Farley

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So let's get something out of the way first. You may know it, but others do not.

Temperature has absolutely ZERO effect on salinity.

OK, that said, temperature does mess with many of the ways that reefers use to measure salinity, and some of these automatically correct for temperature issues, and some do not.

The Hanna corrects for temp issues, although whether it does that correctly or not , I do not know. You can test that by using it to check the salinity of tank water, then let it cool to room temp and check again without changing the device.

Some refractometers have ATC and correct for temp issues, and some do not. Does yours say it has ATC?

Topping off with seawater is the best way to raise salinity, but it can take a week or two or more to get there, depending on amount evaporated daily.
 
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adamf83

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Have you calibrated your refractometer? There are a few threads here on how to make your own DIY calibration solution.

From what I have read, temp should not play a role in salinity readings. Personally, I mix my SW at tank temp. I know there are many people here who mix theirs cold. Perhaps they can offer something to help with that specific issue.

I don't know if the Hanna checker can be calibrated or not. If it can, I would suggest that you calibrate them both and then see where that gets you.

As for raising your salinity, I believe you are doing it the right way. Better to go slowly with that as to avoid stress on your stock.
I calibrated the refractometer with solution I had, it’s reading 1.026. The Hanna can be calibrated with the solution they sell.
So let's get something out of the way first. You may know it, but others do not.

Temperature has absolutely ZERO effect on salinity.

OK, that said, temperature does mess with many of the ways that reefers use to measure salinity, and some of these automatically correct for temperature issues, and some do not.

The Hanna corrects for temp issues, although whether it does that correctly or not , I do not know. You can test that by using it to check the salinity of tank water, then let it cool to room temp and check again without changing the device.

Some refractometers have ATC and correct for temp issues, and some do not. Does yours say it has ATC?

Topping off with seawater is the best way to raise salinity, but it can take a week or two or more to get there, depending on amount evaporated daily.
It does have a big ATC sticker on it. I had no idea that’s what it meant. You learn something everyday!

I’ll take some tank water, let it cool and read it again.

I guess what I could be seeing is 2 devices auto correcting temperatures in a different way? Or I’m just being impatient when it comes to raising the salinity.
 

Jedi1199

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I calibrated the refractometer with solution I had, it’s reading 1.026. The Hanna can be calibrated with the solution they sell.

It does have a big ATC sticker on it. I had no idea that’s what it meant. You learn something everyday!

I’ll take some tank water, let it cool and read it again.

I guess what I could be seeing is 2 devices auto correcting temperatures in a different way? Or I’m just being impatient when it comes to raising the salinity.

DT: Hanna = 1.022 (27.9 Celsius), Refractometer = 1.026
Sump: Hanna = 1.022 (27.9 Celsius), Refractometer = 1.026
Top Off Salt Water: Hanna = 1.029 (21.5 Celsius), Refractometer = 1.031
Distilled Water: Hanna = 1.000 (21.4 Celsius), Refractometer = 1.000


If you want peace of mind, I will say go ahead and calibrate the Hanna. The 2 are not THAT far off, but again just for peace of mind... I have also read that some checkers can go out of calibration over time. It would probably be a good idea to make a calibration check part of your monthly routine.
 
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Randy Holmes-Farley

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Just for understanding the slowness of the process, if you are at sg = 1.020 and replace evaporated water with 1% or 2% of the tank volume each day with 35 ppt (sg = 1.0264) seawater, this is what you get:

Day 1% evap 2% evap
1 1.0200 1.0200
2 1.0203 1.0205
3 1.0205 1.0211
4 1.0208 1.0216
5 1.0211 1.0221
6 1.0213 1.0226
7 1.0216 1.0232
8 1.0218 1.0237
9 1.0221 1.0242
10 1.0224 1.0248
11 1.0226 1.0253
12 1.0229 1.0258
13 1.0232 1.0263
14 1.0234 1.0269
15 1.0237 1.0274
16 1.0240 1.0279
17 1.0242 1.0284
18 1.0245 1.0290
19 1.0248 1.0295
20 1.0250 1.0300
21 1.0253 1.0306
22 1.0255 1.0311
23 1.0258 1.0316
24 1.0261 1.0321
25 1.0263 1.0327
26 1.0266 1.0332
 

thatmanMIKEson

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Just for understanding the slowness of the process, if you are at sg = 1.020 and replace evaporated water with 1% or 2% of the tank volume each day with 35 ppt (sg = 1.0264) seawater, this is what you get:

Day 1% evap 2% evap
1 1.0200 1.0200
2 1.0203 1.0205
3 1.0205 1.0211
4 1.0208 1.0216
5 1.0211 1.0221
6 1.0213 1.0226
7 1.0216 1.0232
8 1.0218 1.0237
9 1.0221 1.0242
10 1.0224 1.0248
11 1.0226 1.0253
12 1.0229 1.0258
13 1.0232 1.0263
14 1.0234 1.0269
15 1.0237 1.0274
16 1.0240 1.0279
17 1.0242 1.0284
18 1.0245 1.0290
19 1.0248 1.0295
20 1.0250 1.0300
21 1.0253 1.0306
22 1.0255 1.0311
23 1.0258 1.0316
24 1.0261 1.0321
25 1.0263 1.0327
26 1.0266 1.0332
Are you telling me thats just math?
 
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