Salinity - SG or PPT?

hkgar

hkgar

Member
Which is more important to look at. Since salinity SG is influenced by temp but PPT is constant shouldn't we look more at PPT?
My SG is about 1.028 yet PPT is 35. I often read that we should keep salinity at 1.022 or 35 PPT.
Should I reduce the SG or maintain the PPT of 35.
Let's have a discussion (debate?)
 
flower

flower

Well-Known Member
Originally Posted by hkgar
http:///forum/post/3216056
Which is more important to look at. Since salinity SG is influenced by temp but PPT is constant shouldn't we look more at PPT?
My SG is about 1.028 yet PPT is 35. I often read that we should keep salinity at 1.022 or 35 PPT.
Should I reduce the SG or maintain the PPT of 35.
Let's have a discussion (debate?)

You either measure with a refractometer PPT or an hydrometer SG. Hydrometer should read no higher than 1.026 which is (according to my book ocean SG).
The SG count will also have a certian PPT count. I use a hydrometer so I don't know off hand the right PPT number that matches it...35???
A refractometer is more accurate, so even if your hydrometer says a certian number 1.028, I would trust the refractometer reading.
 
hkgar

hkgar

Member
I use a refractometer to measure salinity. When i used to use a hydrometer, I had a conversion chart for SG to PPT based on water temp. If you aren't using a refractomter, I strongly suggest getting one. I couldn't believe the amount the hydrometer was off when I switched.
 
bang guy

bang guy

Moderator
Originally Posted by hkgar
http:///forum/post/3216056
Which is more important to look at. Since salinity SG is influenced by temp but PPT is constant shouldn't we look more at PPT?
My SG is about 1.028 yet PPT is 35. I often read that we should keep salinity at 1.022 or 35 PPT.
Should I reduce the SG or maintain the PPT of 35.
Let's have a discussion (debate?)
35 - 37ppt is the salinity of natural seawater where reefs are thriving. That is what I recommend.
 
noah's nemo

noah's nemo

Member
That is the article,but its a BIG NO,NO to put the link up,thats why i went the google route.SO what did you think of it,anyway?
 
hkgar

hkgar

Member
I don't think it is a no no to post links to informative articles, so I am posting this link to an article that showas the sg conversion based on water temp. It states that hydrometers are calibrated to 60f. If you use a hydrometer you should be aware of the change based on temp.
http://www.algone.com/salinity.php
The article was interesting and seems to have some objective testing, or at least observations, and - who knows - might be a change of thinking.
 
king_neptune

king_neptune

Active Member
Originally Posted by hkgar
http:///forum/post/3216056
My SG is about 1.028 yet PPT is 35.
That is inaccurate.
I would trust your refractometer, not your hydrometer.
.0259SG is 35PPT (lets round it up and say .026)
Both my refractometers show SG on the left, and PPT on the right. That way you can read both and don't have to fiddle with a conversion.
 
king_neptune

king_neptune

Active Member
Originally Posted by hkgar
http:///forum/post/3216084
I don't think it is a no no to post links to informative articles,
Exactly. People get too crazy with posting of links rule.
In the ToS we agreed no posting links to competitor sites. A document,journal, or chart is NOT a competitor. Its knowledge.
 
spanko

spanko

Active Member
Not just competitor, sites with other forums and I think there are a couple of more qualifiers.
 
bang guy

bang guy

Moderator
Originally Posted by King_Neptune
http:///forum/post/3216289
.0259SG is 35PPT (lets round it up and say .026)
The specific gravity will vary with temperature so 1.026 is only 35ppt when the tank temp is 68F. At normal reef temperatures, say 82F, 35ppt is a specific gravity of 1.024.
I agree with what you're saying though about trusting the refractometer over the hydrometer.
 
geoj

geoj

Active Member
Just to keep things clear so we don’t come away with any misconceptions. Hydrometers and refractometers measure density (specific gravity) 1.024 g/cm3. Many refractometers automatically compensate for water temperature and can read a conversion to salinity.
A salinometer measure electrical conductivity expressed in salinity as parts per thousand (ppT) or per mil symbol (0/00).
 
king_neptune

king_neptune

Active Member
Originally Posted by GeoJ
http:///forum/post/3216382
Many refractometers automatically compensate for water temperature and can read a conversion to salinity.
I would recommend Milwaukee.
I own two, and they both have ATC(Automatic Temp Control)
Yes, its over kill, but I can always confirm what one says by looking into the other. I used to keep mine at 35ppm, but lately Ive been doing 33-34ppm(.025)
Its good practice to calibrate using distilled water. I have only had to adjust it once in the last 6 months, when I first got it. So its safe to say they are pretty accurate.
*edit:
I check with a few drops of distilled water every couple weeks. But it never needs adjusting.
 
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