Refractometer

golgi aparatus

golgi aparatus

Member
Ok,
So I just got the refractometer from SWF.com. I can read both SG and salinity.
What should my reading be? What is the general consensus as to what my SG and salinity readings should be?
I keep my tank at a constant 80 degrees FYI.
Thanks
 
miaheatlvr

miaheatlvr

Active Member
Originally Posted by Golgi Aparatus
Ok,
So I just got the refractometer from SWF.com. I can read both SG and salinity.
What should my reading be? What is the general consensus as to what my SG and salinity readings should be?
I keep my tank at a constant 80 degrees FYI.
Thanks
S.G should be closer to 1.022 for fish only and closer to 1.025-1.026 for corals and inverts
 
bang guy

bang guy

Moderator
Originally Posted by Golgi Aparatus
What should my reading be?
For a reef tank it should be between 35ppt and 37ppt. This is listed on the 0/000 scale that's on the right side for most refractometers.
You can ignore the S.G. scale.
 
vti eg6

vti eg6

Member

Originally Posted by Golgi Aparatus
OK, thanks.
How about a Fish Only tank?
What should the SG reading be?

Originally Posted by MiaHeatLvr
S.G should be closer to 1.022 for fish only
 
golgi aparatus

golgi aparatus

Member
Originally Posted by Bang Guy
For a reef tank it should be between 35ppt and 37ppt. This is listed on the 0/000 scale that's on the right side for most refractometers.
You can ignore the S.G. scale.

What do you mean about ignoring the S.G. scale?
What should the salinty reading be for a fish only tank?
 
bang guy

bang guy

Moderator
Hydrometers measure Specific Gravity. People use them because they are cheaper than refractometers or meters. When you use a hydrometer you have to also measure the temperature and look on a chart for the Salinity. Salinity should be 35ppt - 37ppt for reef animals.
Refractometers measure Salinity using refraction. They do not and cannot measure Specific Gravity. I have no idea why they put a S.G. scale on a refractometer, ignore it.
Keep Salinity between 35ppt and 37ppt.
 
golgi aparatus

golgi aparatus

Member
Ok. Thanks. My reading on my refractometer is 32 ppm. I have a fish only tank. Should I raise the salinity to 35-37ppm for fish only?
 
bang guy

bang guy

Moderator
Originally Posted by Golgi Aparatus
Ok. Thanks. My reading on my refractometer is 32 ppm. I have a fish only tank. Should I raise the salinity to 35-37ppm for fish only?
There are many opinions on this.
Many believe the lower salinity discourages parasites, this is true but it will not eliminate the most common parasites, Scale Flukes & Ich.
Many believe that the lower Salinity is less stressful for osmoregulation in fish. This is not true except for Brackish fish.
Many, like myself, believe lower salinity is fine for fish larvae but not for adult fish.
I have never had a fish only tank but my fish tend to live longer than their expected lifespan and I keep my salinity around 35-36ppt.
Your tank your choice.
 
golgi aparatus

golgi aparatus

Member
So just to clear things up, my refractometer was purchased from this site and is said to have ATC. Therefore, should my refractometer be able to measure Salinity (ppm) accuratly no matter the water temp?
I know that if my refractometer gives me an accurate salinity, I can then use the chart to finde S.G. based on temp.
Am I on the right track here??
This can be so confusing!
 
darknes

darknes

Active Member
Originally Posted by Golgi Aparatus
So just to clear things up, my refractometer was purchased from this site and is said to have ATC. Therefore, should my refractometer be able to measure Salinity (ppm) accuratly no matter the water temp?
I know that if my refractometer gives me an accurate salinity, I can then use the chart to finde S.G. based on temp.
Am I on the right track here??
This can be so confusing!

You could, but why bother? To me, it's much easier to keep track of the salinity. Especially if your tank has temperature swings, the salinity could be constant, but the SpecificGravity is going to fluctuate (slightly).
Also, salinity is in ppt (parts per thousand), not ppm (parts per million). 35ppm is basically freshwater.
 
bang guy

bang guy

Moderator
Originally Posted by Golgi Aparatus
So just to clear things up, my refractometer was purchased from this site and is said to have ATC. Therefore, should my refractometer be able to measure Salinity (ppm) accuratly no matter the water temp?
I know that if my refractometer gives me an accurate salinity, I can then use the chart to finde S.G. based on temp.
Am I on the right track here??
This can be so confusing!

I agree with the Darknes.
Yes, ATC means that the salinity scale is accurate at reasonable water temperatures.
There is no reason at all to know what the Specific Gravity is. Salinity is what matters to fish and corals. IMO just keep the Salinity at or slightly above 35ppt and it will be perfect.
 
golgi aparatus

golgi aparatus

Member
Great, thanks alot! I really appreciate the input. I have been keeping my salinity at 35 ppt on the refractometer. I appreciate the concise answers. Sometimes, I can get more confused that I began after the answers I get around here!!
 
lexluethar

lexluethar

Active Member
OH crap! So do not use the left side of the refractometer scale? That is what i've been using! I was confused because even thought my salt said it should take X amount of scoups to make the salinity 1.022, it was doing that and it was A LOT lower than that. Why don't they explain the difference and to use salinity...
God you guys are right this is confusing!
 
bang guy

bang guy

Moderator
Originally Posted by LexLuethar
Why don't they explain the difference and to use salinity...
Refractometers used to be the most common way hobbiests measured Salinity. Then in the early 80's Glass hydrometers became popular followed by the plastic swing-arm hydrometer. Hobbiests used the hydrometer and a thermometer and then looked up the Salinity on a chart using the temperature and the Specific Gravity. We didn't know how inaccurate the swing-arm were and they became popular. Eventually, stores would only discuss the specific gravity, then hobbiests followed suit, and then salt manufacturers followed the hobbiests in only referencing Specific Gravity and then completely ignoring Salinity.
New hobbiests started complaining that they had to look up the Specific Gravity on a chart because refractometers only had a Salinity scale. So, to make the customers happy Refractometers started showing up with a Specific Gravity scale.
It's so backwards that it would be funny if it didn't mislead new hobbiests so badly.
Refractometers cannot measure Specific Gravity and even if they did it's Salinity that is the important parameter, not how dense the water is.
 
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