Salinity Testing Issue - Please Help!

[Randy Holmes-Farley]

You had listed some viable models at one point. If I remember, you have some rather expensive devices?

Yes, I had a high end Orion model 128 and 4 electrode probe. In the years since I last had a tank, the probe got cracked somehow and was wonky. I tried to get probes from ebay, but each was a bust since I was cheaping out and trying to get ones that I hoped would work. None did, at least not for seawater salinity. I think one is good for ro/di. Working ones are hundreds of dollars.

Anyway, I found my old American Marine Pinpoint, which I always thought was good, but it was slower to respond than my Orion. I think that is a temp equilibration issue. But for now, I'm using just the Pinpoint, checked in calibration fluid.

Pinpoint

 

[MnFish1]

A quality glass hydrometer is factory calibrated. You can verify it against another calibrated device if you want, but it won’t ever drift or change. Once it’s verified (if you even feel the need), it never needs to be checked again. That makes it a true physical standard.

Yes - I misunderstood the brand of hydrometer he was using - I thought it was one of the 'cheap' brands as compared to a more reliable source.

Also, the hydrometer is not temperature-dependent in the problematic sense. A simple lookup table gives you accurate temperature compensation.

True

A visual refractometer must be calibrated against a standard, and despite what “automatic temperature correction” claims suggest, it’s not truly temperature-compensated. On top of that, its accuracy depends entirely on the precision of the calibration solution. Therefore, your total error is the device’s own margin, plus the human factor in calibration, plus any deviation in the fluid.

A refractometer is not a standard, it is a test instrument that must be calibrated against a standard.

A calibrated refractometer can be used as a standard - but of course it does have to be calibrated. By standard - I meant if you have a couple measurements on different instruments - you can use a refractometer. I didn't mean to imply that a refractometer was a 'gold standard'. But - either way - I think we're in agreement.

 

[Jay Hemdal]

Hey guys!

I think this is the best section to ask this, RHF please move if appropriate :)

This is one of those very humbling things, I feel as though I’ve made a noob mistake (not that I think of myself as much more), and I’m not sure the best course of action, at least in the short term.

Backstory: I don’t have a typical refractometer currently, but about 18 months or so ago I bought a brand new Milwaukee digital refractometer, and I loved it. I calibrated it with distilled water and confirmed with prepared 35 ppt calibration fluid that came with the Milwaukee refractometer, and never gave it much more thought. It has been pointed out to me that it’s not the most accurate option we have, but the darn thing is so convenient, I loved using it, and I assumed it was good enough for what I was doing. At the time, I had two small tanks with some simple Zoas, shrooms, and gorgonians. I continued to occasionally recalibrate with distilled, but I neglected to confirm with a 35 ppt standard. And admittedly, I hadn’t recalibrated it at all in some time now.

More recently, I started a new 25 gallon, and wanted to try some stony corals. I ordered a small batch of frags from Tidal Gardens, delivered yesterday. I decided to test the water the frags came in, and with my Milwaukee they were in 38 ppt water. That seemed odd to me, I would think a place like Tidal Gardens would be right on with salinity, and certainly not high. So right there I started to doubt my Milwaukee. But in the interest of time, I started to slowly acclimate the corals to my tank water.

I also have a Hanna HI98319 Salinity Checker that I got used, if that’s important (perhaps it was incorrectly stored??). I calibrated the Hanna using Hanna’s 35 ppt packets (also came used, but sealed and not expired). I recalibrated the Milwaukee with distilled water. Now when I test my tank water, the Milwaukee reports 33 ppt and the Hanna reports 36.1 ppt. I’ve repeated both tests several times.

What’s really puzzling is that I poured a freshly opened Hanna 35 ppt packet on the Milwaukee, and the Milwaukee is reading that as 25 ppt. I did it three times, each time 25 ppt.

So what gives, and what do I do from here? Sadly, I believe I have frags dying in less than 24 hours, which may be due to other factors, but I have to believe this salinity testing confusion is the root of much of my troubles here :disappointed-face:

Would you be more likely to trust either of the two devices here more than the other?

Yes, I know I need a standard, and yes I’m going to order the TM glass hydrometer and a 500 mL graduated cylinder (should have had one on hand long ago), but that won’t be here until next week, likely. I do like the option of an analog standard that does not need special storage or calibration, and I can use the graduated cylinder to make Randy’s DIY 35 ppt standard solution going forward.

I think my choices right now are:

• Trust one of my two salinity testers
• Run 5 minutes to the pet store near me and grab a swing arm hydrometer
• Drive the 40 minutes or so each way to have a real LFS test the water
• EDIT: I have a PetCo near me that stocks the Imagitatrium refractometer

And, I feel like an idiot, I strongly believe that salinity is the number 1 parameter to stay on top of, and now this.

What would you guys do? Any help would be greatly appreciated! Thank you in advance!

Years ago, I had this exact same issue with refracts and their standard solutions, as well as swing arm hydrometer calibration. I was getting readings all over the place - consistent, but not matching each other. In the end, I used my German lab hydrometer as my standard and adjusted from that. I was so frustrated that I ended up writing it out as an article:

Measuring Salinity / Specific Gravity in Aquariums

This article gives an overview of measuring specific gravity / salinity in aquariums.

www.reef2reef.com

 

[Fish Fan]

Years ago, I had this exact same issue with refracts and their standard solutions, as well as swing arm hydrometer calibration. I was getting readings all over the place - consistent, but not matching each other. In the end, I used my German lab hydrometer as my standard and adjusted from that. I was so frustrated that I ended up writing it out as an article:

Measuring Salinity / Specific Gravity in Aquariums

This article gives an overview of measuring specific gravity / salinity in aquariums.

www.reef2reef.com

Thank you for your reply and help share! I’ll be sure to read the article you linked.

 

[ReefQuestCorals]

Thank you for your help here! I've used those refractometers a lot over the years, and at this time I don't have one, and don't really want one now that I've confirmed that my Milwaukee is working well. I much prefer having a digital readout rather than squinting at anything, especially now that my eyes are not so great. But I appreciate your suggestions, thank you again for your reply and help!

Definitely! Glad you figured out the issue either way

 

[Fish Fan]

Definitely! Glad you figured out the issue either way

I appreciate that! Thank you again for your help here!

 

[BZOFIQ]

Yes, I had a high end Orion model 128 and 4 electrode probe. In the years since I last had a tank, the probe got cracked somehow and was wonky. I tried to get probes from ebay, but each was a bust since I was cheaping out and trying to get ones that I hoped would work. None did, at least not for seawater salinity. I think one is good for ro/di. Working ones are hundreds of dollars.

Anyway, I found my old American Marine Pinpoint, which I always thought was good, but it was slower to respond than my Orion. I think that is a temp equilibration issue. But for now, I'm using just the Pinpoint, checked in calibration fluid.

Pinpoint

I always relied on this and it was pretty darn accurate but I found the reading to be off because of interference with certain pumps. Now I've learned to take a cup of water out to measure. I actually have few.


Also picked up a milwaukee recently which is spot on with my 0 and 35 standards. I calibrate before each use.
I hope it lasts!