Which salinity reading is right?!

[DS204]

About 1 year ago we got our first saltwater setup which was a simple, fluval 13.5 nano tank. We kept two fish in the tank for the last year and used Red Sea blue bucket and Aquaforest salt over that year. The fish remained healthy and happy and we performed weekly water changes.

We measured the salinity regularly and used a Red Sea refractometer. We calibrated it once a month or so using RODI water as per the instructions, to "zero" it out. We kept the salinity at a pretty constant 32 ppt for the year we had this tank, and still have it going.

Fast forward to a few months ago, and we finally setup a large 110g saltwater tank, and cycled it from our nano tank that we had going the past year. We setup the saltwater to be 32ppt as per the Red Sea refractometer.

A short time later, we added a neptune apex system and neptune salinity probe. We calibrated the neptune probe exactly as per the instructions through the app (which if I recall asked me to soak the solution in the sump to bring to temperature) and then calibrated using the neptune 53u (35ppt) solution.

Much to our surprise, the neptune probe is showing a steady reading of 37ppt in the 110g which is 5 higher than our Red Sea refractometer shows. When we filled and checked the tank using the Red Sea refractometer it showed 32ppt. So we have an apparent difference of 5ppt.

Not knowing which to trust, we purchased a Hanna Digital salinity checker (HI98319) and calibrated that as per the instructions, using their calibration solution, and not soaking it in the sump as the directions did not call for that.

After calibrating the Hanna checker it shows the 110g tank as 32ppt as well, which is the same as the Red Sea refractometer. So at this point I wonder if the neptune probe is out, or I calibrated it wrong. We plan to pick up another neptune calibration solution sachet and try to re-calibrate the neptune probe, but just wondering if anyone else can provide some insight of which to trust??

We are basically out by 5ppt. The Hanna checker and Red Sea refractometer show 32ppt, and the neptune probe shows 35ppt.

Please help!!

 

[smartwater101]

Never Never Never trust the Apex salinity probe. Some don't have issues with it. Most do. Its notorious for being finicky.

What hanna checker are you using? The big one or the handheld? I've been using the larger one for over a decade and its been great. I hear the newer handheld one is great as well. Definitely trust those over the Apex probe.

Edit: I see you posted the model number. sorry missed it the first read through

 

[Nanoreefer4ever]

Get the hanna handheld checker worth the time and effort

 

[lapin]

Get some calibration fluid for your refractometer. It is the best choice in my ipinion to measure salinity

 

[DS204]

Never Never Never trust the Apex salinity probe. Some don't have issues with it. Most do. Its notorious for being finicky.

What hanna checker are you using? The big one or the handheld? I've been using the larger one for over a decade and its been great. I hear the newer handheld one is great as well. Definitely trust those over the Apex probe.

Edit: I see you posted the model number. sorry missed it the first read through

Thank-you for your input! We are using the newer style, handheld Hanna checker. We picked up a cleaner shrimp from the LFS on the weekend and they kept the salnity at 28ppt (a bit low, he admitted). We tested that sample water using the Hanna checker and it was accurate. So basically like you said, the Hanna seems to be the accurate one of the 3 we're using.

Thanks again!

 

[DS204]

Get the hanna handheld checker worth the time and effort

That's the one I have already : ) Model# HI98319

We just weren't sure if that was the salinity reading that we should be trusting or not, and it sounds like it is!

 

[DS204]

Get some calibration fluid for your refractometer. It is the best choice in my ipinion to measure salinity

We picked up some Neptune calibration fluid and I already have 3 pouches of the Hanna calibration fluid.

The problem is, each manufacturer appears to recommend their own calibration fluid even though they're all 35ppt or 53u. So I dunno.

I plan to re-calibrate both the Hanna + Apex probe each using their respective calibration fluids this week or weekend.

 

[DS204]

Never Never Never trust the Apex salinity probe. Some don't have issues with it. Most do. Its notorious for being finicky.

What hanna checker are you using? The big one or the handheld? I've been using the larger one for over a decade and its been great. I hear the newer handheld one is great as well. Definitely trust those over the Apex probe.

Edit: I see you posted the model number. sorry missed it the first read through

Further to your reply, I moved the Apex probe to a cup of RODI water and it showed 0ppt (which was re-assuring). I then moved the apex probe to a different part of my sump, and it spit out a reading of 27ppt. Okay, strange.

Then I moved the apex probe back to RODI water, let it zero out with a 0ppt reading, and then back to it's original location in the probe rack. Now it reads 33ppt. So strange. I put the apex probe back into RODI water, let it show 0ppt on the display again, and then moved it to a THIRD spot in my sump - and now it shows 37ppt.

So the neptune probe went from 37ppt, to 27ppt, to 33ppt, to 37ppt. The Hanna showed the same reading all 4 times that I used it, in 3 different spots in my sump. So yeah, going to rely on the Hanna now

 

[Js.Aqua.Project]

The Apex salinity probes are conductivity probes and will fluctuate depending on multiple things in the environment, including but not limited to:
-Actual Salinity/Conductivity
-Air Bubbles
-Whether the cable is next to a power cord (a lot of people wrap the cord or run it through some conduit)
-Temperature compensation setting on the Apex
-Jupiter's Relationship with Venus
-Gremlins (I told you not to get them wet)
-Interference from solar flares

 

[foxt]

Further to your reply, I moved the Apex probe to a cup of RODI water and it showed 0ppt (which was re-assuring). I then moved the apex probe to a different part of my sump, and it spit out a reading of 27ppt. Okay, strange.

Then I moved the apex probe back to RODI water, let it zero out with a 0ppt reading, and then back to it's original location in the probe rack. Now it reads 33ppt. So strange. I put the apex probe back into RODI water, let it show 0ppt on the display again, and then moved it to a THIRD spot in my sump - and now it shows 37ppt.

So the neptune probe went from 37ppt, to 27ppt, to 33ppt, to 37ppt. The Hanna showed the same reading all 4 times that I used it, in 3 different spots in my sump. So yeah, going to rely on the Hanna now

Any particular reason you wanted to monitor salinity with the Apex in the first place?

 

[DS204]

The Apex salinity probes are conductivity probes and will fluctuate depending on multiple things in the environment, including but not limited to:
-Actual Salinity/Conductivity
-Air Bubbles
-Whether the cable is next to a power cord (a lot of people wrap the cord or run it through some conduit)
-Temperature compensation setting on the Apex
-Jupiter's Relationship with Venus
-Gremlins (I told you not to get them wet)
-Interference from solar flares

HA! Pure gold. I think we narrowed it down to either the solar flares, or the mogwai which we accidentally fed after midnight.. sigh. I should have known better!

Side note - I did read about the cable being near a power cord so we re-routed the cable away from all the other electronics, but just as I suspected - it didn't make a difference. Oddly enough, I was able to get 4 different readings from that neptune probe simply by moving it to different spots in my sump. Always careful to give it a slight 'knock' to loosen any air bubbles, and always sure to 'zero it out' between readings. No improvement. I tried setting the temperature compensation to zero, but no difference. It also says you won't need to adjust the TC if you use automatic calibration (which I did) and if you use a temperature probe (which I do). So this thing leaves me stumped. I'm going to re-calibrate it later, but why should I have to bother with something brand new that's designed for saltwater. I dunno.

My conclusion so far, is that the neptune probe is junk. I'm not done playing with it, and I haven't given up hope on it yet - but for me to require so much tinkering for something that's been carefully calibrated right out of the box, is purely a waste of my valuable time!

 

[DS204]

Any particular reason you wanted to monitor salinity with the Apex in the first place?

Simply because it came with the neptune apex and naturally, we figured it was designed for monitoring salinity in a saltwater aquarium.

 

[foxt]

Simply because it came with the neptune apex and naturally, we figured it was designed for monitoring salinity in a saltwater aquarium.

Ah, I see. I didn't realize that Neptune actually includes them in a version of the Apex bundle. Thanks for taking the time to share your experience!

 

[DS204]

Ah, I see. I didn't realize that Neptune actually includes them in a version of the Apex bundle. Thanks for taking the time to share your experience!

I should have been more clear. We purchased the Neptune Apex package that includes the temperature, salinity, ORA, and ph probes. The salinity probe has proven to be a frustrating experience for us so far, but we will re-visit the problem and re-calibrate it to be sure there's no user error involved.

Thanks for reading!

 

[foxt]

I think you will find that there is no practical need for the salinity probe. Anything that you would want to try to do with it is better done a different way.

 

[Marco S]

I should have been more clear. We purchased the Neptune Apex package that includes the temperature, salinity, ORA, and ph probes. The salinity probe has proven to be a frustrating experience for us so far, but we will re-visit the problem and re-calibrate it to be sure there's no user error involved.

Thanks for reading!

Don't bother trying to re-calibrate...it will always be off. Just use either the Hannah or refractometer and match the correct salinity you want to the salinity the Apex is reading and just use the Apex to monitor swings. For example...if the you want the salinity at 34 ppt and the Hannah is reading 34 ppt and the Apex is reading 37 ppt then you know that 37 ppt is actually 34 ppt and just monitor it and make sure it stays around that 37 ppt on the Apex and all is good. ;Happy

Edit: Figured I would add that my Apex reads 35 ppt as 32 ppt after about 50 calibrations with different brand calibration fluid and moving the probes about 100 times...I gave up finally and accepted that 32 ppt is my new 35 ppt and just monitor it for swings now.

 

[DS204]

I think you will find that there is no practical need for the salinity probe. Anything that you would want to try to do with it is better done a different way.

We are learning that first hand unfortunately, so at this point I tend to agree.

Realistically though, I see myself using the neptune salinity probe solely to measure fluctuations in salinity instead of as an accurate reflection of the true salinity value. We'll use the Hanna for a true baseline and reliable reading.

 

[DS204]

Don't bother trying to re-calibrate...it will always be off. Just use either the Hannah or refractometer and match the correct salinity you want to the salinity the Apex is reading and just use the Apex to monitor swings. For example...if the you want the salinity at 34 ppt and the Hannah is reading 34 ppt and the Apex is reading 37 ppt then you know that 37 ppt is actually 34 ppt and just monitor it and make sure it stays around that 37 ppt on the Apex and all is good. ;Happy

Edit: Figured I would add that my Apex reads 35 ppt as 32 ppt after about 50 calibrations with different brand calibration fluid and moving the probes about 100 times...I gave up finally and accepted that 32 ppt is my new 35 ppt and just monitor it for swings now.

Thank-you for your input. This is most likely what we'll do.

Appreciate everyone chiming in! Information from other people always helps to make a more informed decision.

 

[foxt]

Salinity shouldn't fluctuate that much. The two biggest influencers are evaporation and the mix point of your water when you do water changes. Trying to monitor it with the Apex probe will just leave you chasing phantoms ...

 

[DS204]

Salinity shouldn't fluctuate that much. The two biggest influencers are evaporation and the mix point of your water when you do water changes. Trying to monitor it with the Apex probe will just leave you chasing phantoms ...

Yes, thank you. Fortunately for us the salinity reading has not been fluctuating, and has been steady at 37ppt. Which is probably not an accurate measurement.

We are aware of evaporation and water changes, etc. We are using the built-in red sea ATO at the moment until I can setup the Spectrapure ATO we bought last month. The Red Sea ATO has been rock-solid after I got it dialed-in, much to my surprise. We haven't seen the water level drop even a single millimeter in the last 3 weeks. It's been perfect!

So luckily we aren't chasing phantoms, we're just trying to determine what my salinity truly is. Which I believe, the Hanna is indicating to be accurate... along with the red sea refractometer.