Reef Chemistry Question of the Day #165 Salinity of Skimmate

[Randy Holmes-Farley]

Reef Chemistry Question of the Day [HASHTAG]#165[/HASHTAG]

Something that has come up occasionally over the years is the salinity of skimmate.

Which of the following do you think is likely to be the best way to measure the salinity of a typical reef aquarium skimmate? FWIW, all off these work well for normal seawater.

1. Refractometer
2. Conductivity meter
3. Hydrometer
4. Drying it and measuring the weight

Good luck!






















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[Vance]

Not 100% sure, but i am gonna go with Conductivity meter. Its the only measuring technique I can rationalize that the other products in skimmate doesnt skew the results. Drying is out for sure, to many other DOC's and compounds. Pretty sure refract and hydrometer are out as well for the same reason. Unless a skimmer removes ionized compounds...

 

[goatcorals]

I'm going with conductivity meter too.

 

[jsker]

I am going with choice 3

 

[JimWelsh]

Given the discussion in this thread, I'm going with conductivity, since that is the current standard by which salinity is defined.

 

[TheEngineer]

I say let it settle out and use the refractometer

 

[cb684]

Conductivity meter.

 

[Ontheway]

Refractometer will fail due to other agents changing refraction indice.

Drying will measure salt and organics.

Conductivity meter looks like a good answer, but what about bonded metals? Can they change EC of water? I think it needs something to be homogeniously dissolved in water to alter general electrical conductivity, so looks like this one can be the answer.

Hydrometer measures density which will also fail in skimmate.

 

[Cory]

Id say refractometer as long as the source of light is bright enough.

Fwiw i remember asking you what the salinity of skimmate was and you said "close to the salinity of the tank water".

Actually i change my answer to conductivity because organics would absorb certain colors of light possibly causing interference in the refraction of light.

Do refractometers depend on all colors of light for accuracy?

 

[DeniseAndy]

Mine is never very liquidy, mostly thick gooey brown yuck. So, I guess have to be conductivity cuz nothing seems right.

 

[Myka]

I say let it settle out and use the refractometer

I've done this before, and it works. I'm not sure if it's accurate, but I can get a reading from it. So this is my answer too.

 

[Randy Holmes-Farley]

I've done this before, and it works. I'm not sure if it's accurate, but I can get a reading from it. So this is my answer too.

All of the mentioned methods will produce some type of result.

 

[Bunnee911]

I'll bite. #1. Because, there is not enough to use 3. I don't have 2. And 4 just seems odd.

 

[Lynn52]

Conductivity meter

 

[beaslbob]

4

 

[beaslbob]

no fair

there isn't a C

 

[kevindo123]

Taste it and if it's salty compared to your aquarium water.

 

[Irsug1]

Tea Anyone?!

 

[kevindo123]

The scientific way maybe to do #4

 

[TheEngineer]

All of the mentioned methods will produce some type of result.

So which is it!?