What could have caused an increase in salinity?

[jabeuy]

I recently got a refractometer(atc) and a new skimmer.

 

I tested my water right away, and got 1.024 S.G.

That evening I put in the skimmer. A few days later I tested water again, and got 1.029 S.G.

 

Tested on my QT tank, water is normal at 1.024 and RODI is at 0.

 

The only thing I changed in the tank was adding the skimmer. But as I understand, instead a skimmer would lower salinity if anything.

 

What could have caused this increase? I have an ATO it's been working the whole time. Corals look great and so do the fish. Could it perhaps be a faulty refractometer?

[Angel<3Nanos]

Skimmers don't lower salinity. They increase it.

[jedimasterben]

Skimmers don't lower salinity. They increase it.

Uh. What? http://www.advancedaquarist.com/2010/2/aafeature

[Angel<3Nanos]

Uh. What? http://www.advancedaquarist.com/2010/2/aafeature

Ah I was misguided then. I stand corrected

[DriftingNemo]

Only one explanation..

[joy13]

Calibrate the refractometer.

[jedimasterben]

Calibrate the refractometer.

This. Or buy a floating glass hydrometer.

[jabeuy]

Calibrate the refractometer.

I'll probably get some calibration fluid soon. But I used RODI and calibrated to 0, maybe thats the issue.

 

My swing arm hydrometer also reads slightly higher than normal, so I think salinity definitely went up.

[{8ry}]

Silly question, but you are topping off with RODI water....right? Not saltwater?!

[markalot]

I'll probably get some calibration fluid soon. But I used RODI and calibrated to 0, maybe thats the issue.

 

My swing arm hydrometer also reads slightly higher than normal, so I think salinity definitely went up.

 

No, that introduces calibration error, sometimes a lot of it depending on the device. Even if the instructions say to calibrate with RO/DI they are wrong. The BRS refractometer actually comes with a big orange piece of paper telling you to ignore the directions. Buy some calibration fluid as soon as you can. Also keep in mind you should let the refractometer sit for a minute to temperature calibrate before trusting the reading.

 

And, just to make sure, you are topping off with RO/DI, correct? (woops, just asked above)

[jabeuy]

Haha yup, topping off with RODI

 

Unless someone at home figured out how to mix saltwater and it in the RODI reservoir!

[markalot]

Haha yup, topping off with RODI

 

Unless someone at home figured out how to mix saltwater and it in the RODI reservoir!

 

Probably a testing or calibration error then. Get that 35ppt fluid to calibrate ... or there is a recipe somewhere to make your own.

 

http://www.reefkeeping.com/issues/2004-06/rhf/

 

 

For a rougher measurement in the absence of an accurate water volume or weight measurement:

1. Measure ¼ cup of Morton's Iodized Salt (about 73.1 g)

2. Add 1 teaspoon of salt (making about 79.3 g total salt)

3. Measure the full volume of a plastic 2-L Coke or Diet Coke bottle filled with purified freshwater (about 2104.4 g)

4. Dissolve the total salt (79.3 g) in the total water volume (2104 g) to make an approximately 3.65 weight percent solution of NaCl. The volume of this solution will be slightly larger than the Coke bottle, so dissolve it in another container.

 

[[Notice added post-publication: the standards described here that use Coke bottles are subject to variation in the volume of a 2-L Coke bottle. It has recently come to my attention that such 2-L bottles can vary in total volume, and that this can lead to at least a 1 ppt error in the salinity of the standards matched to seawater salinity of 35 ppt. Standards made with accurate measurements of salt and water should still accurately match 35 ppt.]]

[jabeuy]

 

Probably a testing or calibration error then. Get that 35ppt fluid to calibrate ... or there is a recipe somewhere to make your own.

 

http://www.reefkeeping.com/issues/2004-06/rhf/

 

 

Thanks for the info Mark! I think for all that work, I may as well get some calibration fluid haha. Anyway, right now the tank looks great, so no rush, I'll just get some fluid next time I have a chance.

 

Hope its just calibration issues, otherwise...probably aliens! Lol

[cju84]

Might not hurt to get a hydrometer as well.

[jabeuy]

Might not hurt to get a hydrometer as well.

Yes sir, have both hydro/refractometer. Both show elevated readings, but refractometer more so.

[charnelhouse]

Here's a noob question for you all - Can you use natural seawater as calibration fluid? I should probably Google this before asking it....

[jabeuy]

Here's a noob question for you all - Can you use natural seawater as calibration fluid? I should probably Google this before asking it....

Just off the top of my head, I would think you can use any fluid you know the salinity of. Calibration fluid is just water at a known salinity, so you can adjust the refractometer to match what the fluid "should" be at. Correct me if I'm wrong though.

[charnelhouse]

Just off the top of my head, I would think you can use any fluid you know the salinity of. Calibration fluid is just water at a known salinity, so you can adjust the refractometer to match what the fluid "should" be at. Correct me if I'm wrong though.

 

I guess I should have been more specific. Is seawater known to be 35ppm as long as it is collected from a location where it isn't diluted or standing and subject to evaporation?

[jabeuy]

Got some calibration fluid.

It indeed needed some calibration, but my tank's SG is at 1.027.

 

All corals look great and so do the fish.

 

It must've increased from water changes. Last time I did a PWC all I had was the swing arm hydrometer, so...not as reliable and must be what caused this.