Neptune Apex - Salinity after water change

michaelr7170 · Nov 6, 2016

I am running a 90 gallon with a 35gal sump, and using a 2016 model apex controller. I normally do multiple small water changes rather that less frequent large ones, of approx. 5 gallons at a time.

Due to issues with my refractometer being off, I realized after installing my apex that my salinity was low, around 30-31. I have recalibrate my refractometer properly and now have it matching my apex pretty closely. The last two water changes I've been bringing up my salinity slowly, doing 5 gallon changes with 35 water. After doing so, my apex jumps to 41-42 salinity readings. After the first time I took out my probe, rinsed in RODI and dried, recalibrate and put it back in and the readings were around 32.2, which made complete sense and where it should be after changing that small amount.

Today I did another 5 gal change using the same 35 freshly mixed saltwater and it happened again. Back up to 42.. I don't want to have to keep drying and recalibration my probe after a water change. Any ideas what's going on?

Some info, I have temp compensation of 2.2. Also, when I remove the 5 gal, my salinity probe is suspended in air for the duration until new water is added. I also give it a shake after the change is complete to remove bubbles. Appreciate any input!

Whipples · Nov 11, 2016

In my albeit limited experience with the salinity probe i added the second temp probe to the PM2 module and more often than not my salinity reading is spot on BUT I do not run any temperature compensation as when I calibrated it i did not have the second temp module. If I were you, I would dip the probe in RODI water, give it a gentle shake to make sure you shake out any salt water, and let it dry for a few hours. Recalibrate in 35ppt solution with the temperature probe in the solution at your display tank temperature and it should be rock solid after that. If it isn't there is something else at play like potential interference. I run my salinity probe wire in a completely different direction away from all of my other electronics. Not necessarily the prettiest, but mine has been rock solid in readings and reads the same as my refractometer.

One issue most folks have is that the probe is VERY susceptible to bubbles so if you have microbubbles in the probe area it can be screwing with the reading.

Also it is very fragile, so be careful when you shake out the bubbles :)

Salty1962 · Nov 12, 2016

Whipples said:
In my albeit limited experience with the salinity probe i added the second temp probe to the PM2 module and more often than not my salinity reading is spot on BUT I do not run any temperature compensation as when I calibrated it i did not have the second temp module. If I were you, I would dip the probe in RODI water, give it a gentle shake to make sure you shake out any salt water, and let it dry for a few hours. Recalibrate in 35ppt solution with the temperature probe in the solution at your display tank temperature and it should be rock solid after that. If it isn't there is something else at play like potential interference. I run my salinity probe wire in a completely different direction away from all of my other electronics. Not necessarily the prettiest, but mine has been rock solid in readings and reads the same as my refractometer.

One issue most folks have is that the probe is VERY susceptible to bubbles so if you have microbubbles in the probe area it can be screwing with the reading.

Also it is very fragile, so be careful when you shake out the bubbles :)

Sometimes my pumps will cavitate and create a lot of micro bubbles. I found I had to shake the probe to workout the bubble that were caught in the tip of the probe to get it to read properly.

michaelr7170 · Nov 29, 2016

Whipples said:
In my albeit limited experience with the salinity probe i added the second temp probe to the PM2 module and more often than not my salinity reading is spot on BUT I do not run any temperature compensation as when I calibrated it i did not have the second temp module. If I were you, I would dip the probe in RODI water, give it a gentle shake to make sure you shake out any salt water, and let it dry for a few hours. Recalibrate in 35ppt solution with the temperature probe in the solution at your display tank temperature and it should be rock solid after that. If it isn't there is something else at play like potential interference. I run my salinity probe wire in a completely different direction away from all of my other electronics. Not necessarily the prettiest, but mine has been rock solid in readings and reads the same as my refractometer.

One issue most folks have is that the probe is VERY susceptible to bubbles so if you have microbubbles in the probe area it can be screwing with the reading.

Also it is very fragile, so be careful when you shake out the bubbles :)

My readings are excellent for the most part UNTIL my salinity probe makes contact with air. Once I place it back in the water, shake it to remove any bubbles, the salinity jumped to 42. This happened twice, there's no bubbles, no change whatsoever except that it made contact with air during a water change. I as well run my wire away from all other electronics. As soon as I recalibrate it's back To normal readings... seems bizarre but I feel like there's something going on here with the air, air temperature, and temperature compensation setting

Whipples · Dec 1, 2016

You may be right, and I know the conductivity probe is particularly susceptible to changes. I try to re-calibrate mine once every few months, same with my pH probes. I re-did it the other day with temperature compensation at 2 versus 2.2 and it has so far been even more solid than before. When I take it out of the water, I shake and let it sit within some RODI for a few minutes to help knock out any excess salt water trapped and then let it sit out in the air for 2-3 hours before i try to re-calibrate.

Also, do you run the second temperature probe? One thing I screwed up early on was picking the wrong temperature probe for the temperature compensation XD.

Js.Aqua.Project · Dec 1, 2016

Don't know why, I am also running the 2016 Apex, but I get the same issue. It normally resolves itself within an hour though.

Every time I top off (don't have an ATO yet but it's in the works) somehow my salinity goes UP. Same for the first hour after my weekly WC.

LittleMaui · Dec 1, 2016

Not sure if this helps,but I too have problems getting reliable salinity readings on my new 2016 Apex. This is what Apex support told me.....

"
Our cond probe will not read number to number identically with milwakee's calibration or any other third party tools for checking this measurement. If you calibrated it properly. In the 53ms solution it should read around 34.8~35.2. If it did read that after you calibrated it than you successfully calibrated the probe. That's what's important. That it read 34.8~35.2 in the calibration solution from Neptune systems.

Can you put the probe back in the 53ms solution and what does it read? If it does not read within that range then calibrate the Cond probe again. If it did, than you're done.

After that, if you drop it in to a tank or any environment it will read what the conductivity is of that tank. It's not going to be the same as your refractometer, hydrometer, or anything. Our probe reads the conductivity. It's not the same.

To clarify, the cond probe functions by measuring the displacement of salt ions in the water. The Conductivity probe is not a refractometer. The conductivity probe reports what it get's back from the submerged liquid it's in. It's not going to read like your refractometer. This is common. It's a conductive sensing probe. Your refractometer is designed to detect different ways so the readings will be close but also different. The refractometer will give you a closer look at the salinity.

Typically most refractometers are not calibrated for Seawater, but a brine solution, thus they are reading the SG/salinity of many other salts in your water other than NaCl. So they will read slightly differently than a conductivity probe which only measures your actual NaCl concentration. Here is ant article on Reef Builders illustrating this discrepancy and points to another article discussing these differences. So it is not uncommon to see this difference between most refratometers and salinity probes."

Whipples · Dec 1, 2016

Where do you guys have your probe located? Mine is in the return section of the sump where the water is the least turbulent and little to no bubbles enter it, and the level is extremely stable.

michaelr7170 · Dec 1, 2016

Whipples said:
You may be right, and I know the conductivity probe is particularly susceptible to changes. I try to re-calibrate mine once every few months, same with my pH probes. I re-did it the other day with temperature compensation at 2 versus 2.2 and it has so far been even more solid than before. When I take it out of the water, I shake and let it sit within some RODI for a few minutes to help knock out any excess salt water trapped and then let it sit out in the air for 2-3 hours before i try to re-calibrate.

Also, do you run the second temperature probe? One thing I screwed up early on was picking the wrong temperature probe for the temperature compensation XD.

Nope I don't use the second temp probe! I've been getting by with just making sure when I do a water change my salinity probe stays submerged.. if it touches air unfortunately that requires re-calibration.

michaelr7170 · Dec 1, 2016

Js.Aqua.Project said:
Don't know why, I am also running the 2016 Apex, but I get the same issue. It normally resolves itself within an hour though.

Every time I top off (don't have an ATO yet but it's in the works) somehow my salinity goes UP. Same for the first hour after my weekly WC.

I've left mine for a full day and still didn't correct itself unfortunately :(

michaelr7170 · Dec 1, 2016

shaywood said:
Not sure if this helps,but I too have problems getting reliable salinity readings on my new 2016 Apex. This is what Apex support told me.....

"
Our cond probe will not read number to number identically with milwakee's calibration or any other third party tools for checking this measurement. If you calibrated it properly. In the 53ms solution it should read around 34.8~35.2. If it did read that after you calibrated it than you successfully calibrated the probe. That's what's important. That it read 34.8~35.2 in the calibration solution from Neptune systems.

Can you put the probe back in the 53ms solution and what does it read? If it does not read within that range then calibrate the Cond probe again. If it did, than you're done.

After that, if you drop it in to a tank or any environment it will read what the conductivity is of that tank. It's not going to be the same as your refractometer, hydrometer, or anything. Our probe reads the conductivity. It's not the same.

To clarify, the cond probe functions by measuring the displacement of salt ions in the water. The Conductivity probe is not a refractometer. The conductivity probe reports what it get's back from the submerged liquid it's in. It's not going to read like your refractometer. This is common. It's a conductive sensing probe. Your refractometer is designed to detect different ways so the readings will be close but also different. The refractometer will give you a closer look at the salinity.

Typically most refractometers are not calibrated for Seawater, but a brine solution, thus they are reading the SG/salinity of many other salts in your water other than NaCl. So they will read slightly differently than a conductivity probe which only measures your actual NaCl concentration. Here is ant article on Reef Builders illustrating this discrepancy and points to another article discussing these differences. So it is not uncommon to see this difference between most refratometers and salinity probes."

Whoa that's a lot to digest haha - so I assume they are implying that we should only be concerned with the NaCl content and not the total salt content that a refractometer measures? I.e. Refractometer will probably be a little higher than the conductivity probe due to measuring other salts as well, so we should aim for ~35ppt on our probe readings and forget the rest..

michaelr7170 · Dec 1, 2016

Whipples said:
Where do you guys have your probe located? Mine is in the return section of the sump where the water is the least turbulent and little to no bubbles enter it, and the level is extremely stable.

Same, return section where the water is stagnant. Also have my probe chord isolated from any electrical interference from other equipment/chords

LittleMaui · Dec 1, 2016

I have to admit I'm confused. I thought most people could get their refractor and probe numbers to match. I have tried a couple places in my sump, but still get inconsistent numbers. For example, after a reading of around 32, last night I simply shook the probe around and moved it back. Then got a reading of 38, which is pretty much where it is staying, but it's in the same location I was getting 32. Strange. I will say Apex support has been very quick to respond with suggestions.

Can anyone explain the different between APEX's automatic calibration and manual? What the temp compensation all about?

Scott.h · Dec 8, 2016

My calibrated refractometer is spot on 1025 and my calibrated probe reads around 36.6. Both are calibrated correctly. I trust my refractometer. I keep my magnesium at about 1350, so I do wonder if one were to manipulate magnesium if it would sway one tool or the other.

I've heard lots of people having issues with their probes being all over the place.

michaelr7170 · Dec 12, 2016

So I re-calibrated again tonight, both my refractometer (using two different solutions of 1.026 fluid, both align) and my salinity probe.

After calibration my refractometer is showing a reading of 35 ppt in my aquarium.

My salinity probe is giving a reading of 32.6-33.0, which it was also giving before calibration as well.

SO - I want my salinity at 35ppt, should I trust my refractometer and assume my salinity is spot on?! Or should I assume my refractometer is reading high, and up my salinity until my probe reads 35.

Scott.h · Dec 12, 2016

I actually turned mine off today. Got tired of my alarms. Every week the reading consistently goes up. If it were correct everything in my tank would probably be dead. I even broke out the old glass bobber just to make sure my refractometer wasn't bad. Which read 1.022 compared the the 1.025 of the refractometer. I think the probe read 38.9 today. Junk. It's a month old and I'm certainly not recalibrating it once a week. It's in the return chamber of the sump. No bubbles and no real turbulence. Waste of money

Js.Aqua.Project · Dec 12, 2016

michaelr7170 said:
So I re-calibrated again tonight, both my refractometer (using two different solutions of 1.026 fluid, both align) and my salinity probe.

After calibration my refractometer is showing a reading of 35 ppt in my aquarium.

My salinity probe is giving a reading of 32.6-33.0, which it was also giving before calibration as well.

SO - I want my salinity at 35ppt, should I trust my refractometer and assume my salinity is spot on?! Or should I assume my refractometer is reading high, and up my salinity until my probe reads 35.

I know that depending on temp a refractometer can get a slightly different reading, maybe this is part of the issue?