Temp and Salinity

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redsea reefer

Well-Known Member
I used to mix my fresh SW in a 5g bucket using a small 100 gph power head and the temp was 79 degrees after a day or two circulating. I now use my old protein skimmer pump rated at 300 gph to aerate the water and more circulating power, now the temp has increased to 82 degrees.

Will this increase in temperature give me a false salinity reading(+/-) on my refractometer, it is a Automatic Temp Compensating model...

Thanks on advance...:)
 
chipmunkofdoom2

chipmunkofdoom2

Well-Known Member
I think "temperature correction" is a feature inherently included in the design of a refractometer. The two or three drops of water you put on the lens will equalize very quickly to room temperature, so as long as you've calibrated it to read 0.000 with freshwater at room temperature, then as soon as the saltwater becomes room temp, the reading should be accurate.
 
R

redsea reefer

Well-Known Member
Ok, lets forget about the refractometer a sec...

So, If I get two buckets filled with 5g of water with the same amount of salt dissolved in each but one was 79 degrees and the other 82, now if a check them with a digital high end salinity meter, would they have the same reading.
 
Dweezil

Dweezil

Well-Known Member
In my experience it does change with temp. However, I have not done a real scientific test. I just know that I have tested at various temps and it does change.
 
Dweezil

Dweezil

Well-Known Member
Yes I did. I was thinking along the same lines as you. I mixed up a bucket of water and started testing at different temps and they were definately different.
 
R

redsea reefer

Well-Known Member
OK, thanks Dweezil...:) I'm gonna do that too, This week I'll make my water with the small powerhead and compare it to my last batch...
 
Clownfish518

Clownfish518

Razorback
PREMIUM
For a given SG, salinity will vary with temperature.

The math gets complicated; conversion charts are easy to find
 
Boomer

Boomer

Reef Sanctuary's Mr. Wizard
Salinity from a refract, conductivity meter or hydrometer always varies with temp because cold water is denser than warm water, so it has to change. If you made a bucket up of seawater, got a reading at 77 F and raised the temp to 82 F it will not be the same. Now does the actual Salinity change, that 35 ppt, 31 ppt , etc. will not change. There are Salinity test kit for this if you want to use one. It is only instruments that do this, which are affected by temp, as they cannot measure actual salt in the water but can give reality value, which must be correct
for temp. So, with instruments try to measure at the temp you want it at. Electronic meters and ATC refract correct to a std temp of 25 C.

So, with all that crap said you refract is fine as it has ATC
 
tnwillia

tnwillia

Well-Known Member
I use the Pinpoint Salinity monitor. I watch this happen in "real time" as both temp change and salt is added as I mix water. I don't use a refractometer so I can't go there.
 
B

BobBursek

Active Member
And, refractometers SHOULD Not be calibrated to zerro using pure water, they will read "off" at salt water at 1.0265/ 35ppm. they need to be calibrated at that level with pinpoint 53 solution to be accurate at that level.
 
R

redsea reefer

Well-Known Member
Boomer said:
Salinity from a refract, conductivity meter or hydrometer always varies with temp because cold water is denser than warm water, so it has to change. If you made a bucket up of seawater, got a reading at 77 F and raised the temp to 82 F it will not be the same. Now does the actual Salinity change, that 35 ppt, 31 ppt , etc. will not change. There are Salinity test kit for this if you want to use one. It is only instruments that do this, which are affected by temp, as they cannot measure actual salt in the water but can give reality value, which must be correct
for temp. So, with instruments try to measure at the temp you want it at. Electronic meters and ATC refract correct to a std temp of 25 C.

So, with all that crap said you refract is fine as it has ATC
Click to expand...

Thanks Boomer, thats the answer I was looking for.
 
Boomer

Boomer

Reef Sanctuary's Mr. Wizard
Eddie

That ATC is not good for any temp. Do not go beyond +/- 5 F . I would try to sty +/- 2 F. If you are thinkin' "I want to dissolve the salt @ 90 F as it is faster " and then let it cool down to 75 F it is going to be off.
 
R

redsea reefer

Well-Known Member
Boomer said:
Eddie

That ATC is not good for any temp. Do not go beyond +/- 5 F . I would try to sty +/- 2 F. If you are thinkin' "I want to dissolve the salt @ 90 F as it is faster " and then let it cool down to 75 F it is going to be off.
Click to expand...

No, thats not what I was thinking. I just started using a big skimmer pump to aerate/circulate fresh SW in my 5g bucket and temp rose by 3 degrees F.

Do you know of a good link for a temp/salinity conversion chart by any chance.
 
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