Salinity

[fachatga]

So this tool tells me 1.0275 or so and yes I just calibrated it.

Then I put this in the water and it says 1.0245. Should I be seeing such a big difference?

I’m just wondering if my salinity has been way off until now. I’m measuring my new saltwater in a trash can after I turned off the powerhead. So I’m getting a good reading with the second tool. I just got it. I thought it would be more accurate since no reliance on calibration fluid and never needs calibration. Should I slowly adjust my salinity up so it’s 1.025-6 on that second one? I get confused on which are called what.

 

[Gtinnel]

The top one is a refractometer and the bottom is a glass or floating hydrometer.
Usually you are right the hydrometer is generally considered the most accurate way to measure salinity.
What did you calibrate the refractometer with? I wouldn't start making changes until you are positive what your salinity is.

 

[ZoWhat]

Refractometer Calibration Solution

Keep your refractometer readings accurate! A refractometer is easily one of the most important tools to have if you own a saltwater tank. Without a refractometer, we would be guessing at how much salt is in the water, and more than likely would not be correct! Even if you have a refractometer...

www.bulkreefsupply.com

 

[fachatga]

I use this to calibrate. I’m also gonna add some plain rodi so I’m not changing anything on this water change Maybe I’ll use one of the recipes on these boards to make my own calibration fluid my tank is doing well even sps is growing But I want to be able to measure it accurately and control what it is. Thanks for the help

 

[Gtinnel]

I use this to calibrate. I’m also gonna add some plain rodi so I’m not changing anything on this water change Maybe I’ll use one of the recipes on these boards to make my own calibration fluid my tank is doing well even sps is growing But I want to be able to measure it accurately and control what it is. Thanks for the help

I think making your own calibration solution to test/calibrate the refractometer is a great idea. If you have any cheap kitchen scales it can be made with table salt for very, very little cost. Sadly I've recieved calibration solutions that aren't exactly the salinity they were supposed to be so I now just make my own. I find that the refractometer that I use, if maintained and periodically calibrated, is incredibly consistent and out of the measuring tools that I have the one I trust most.

 

[fachatga]

I do have a kitchen scale. I’ll try doing that. Can you tell me the recipe that you use?

 

[gbroadbridge]

Calibrate the refrac so it shows 35ppt using the Calibration solution, and then mix your salt water to 35ppt based on that.

Best is to make your own calibration solution using the recipe suggested by Randy.

 

[Gtinnel]

Here is the text copied from the article that Randy wrote on making a test solution for refractometers.
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 fresh water (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.

Here is anlink to the whole article

http://reefkeeping.com/issues/2004-06/rhf/index.htm

Also, I believe if you want to test the hydrometer there is a different recipe in the article

 

[fachatga]

Thank you!

 

[fachatga]

So gonna use the hydrometer from now on. It’s nice and easy. Made the solution and the refractometer read 1.0275 or so. That solution I bought is junk. My tank has been running 1.0225-1.023 since Maybe April. Hard to tell exactly. My eyes can’t read the refraxtometer exactly. Almost Funny they I’ve still had success. I’ll slowly add some saltwater to my top off so it’s maybe a quarter saltwater so it takes a long tome to bring it up. Great to finally know this has been so far off.

 

[Cory]

Are you compensating for temperature of the floating hydrometer?

 

[fachatga]

It says on it to take reading at 77 so that’s what I heated the water to when I did the reading.

 

[Cory]

It says on it to take reading at 77 so that’s what I heated the water to when I did the reading.

Okay. I measure the temperature that the hydrometer is floating in. It changes pretty fast.

 

[Reef.]

It says on it to take reading at 77 so that’s what I heated the water to when I did the reading.

I would trust the hydrometer then.

Have you tried using the hydrometer to get salt water at 35ppt then using that water to calibrate the refractometer, see how long it stays correct.

The only issue you could really get with the hydrometer is if not using a good thermometer to make sure the water is at 77, there are more things to go wrong with a refractometer.

 

[fachatga]

I used one of the temp probes I usually have in a tank. I have like 5 thermometers I’ve used for various things and they’re all within a degree of each other. I put them all in the same tank one day to make sure I’m getting reasonable results. I threw one out that was an outlier so I could have consistent temp readings. I’m really happy I got the hydrometer now. Can’t believe I was so far off. Hope somebody else also reads this and checks their calibration liquid too.

 

[Reef.]

If it’s a tropic Marin, check it’s the marine one as believe they do a couple of different models, one of them (the German one they measure differently) you will be aiming for a lower reading to get an actual reading of 1.0264

 

[fachatga]

yeah. It’s this one

 

[Reef.]

yeah. It’s this one

Yeah same as mine.

 

[Reef.]

You had the same experience as me, first time I used my hydrometer I thought it was broken as the salinity was so much off, I couldn’t believe my refractometer was as bad as it was.

 

[fachatga]

Lol. I’m feeling much more comfortable having this thing now. At least for my newly mixed water it’s easy to get water to the right temp and use it. I’ve got a graduated cylinder for tank water but it’s warmer. I know there are charts out there though to convert. But once I see what it should be I’ll be able to keep it consistent.