Apex salinity probe! How can I get it working right? Well hopefully this helps.

As the title states I am writing this article to help those of you who are having issues getting your salinity probe to be successful. Do you feel like you just can’t get it right and that you think you’ve done everything possible to make it work. Well I am here to hopefully help you with this issue.

So let’s start by talking about two variables that might affect the probe from functioning properly even before you add a probe to your system.
1. Micro bubbles.


Maybe some of you are asking why would bubbles or micro bubbles even matter. It’s simple really the probe needs full water contact with the sensor and trapped bubbles inside the contact area lessen the sensors ability to get a correct reading.
The first sign you are going to have an issue with micro bubbles is if you see them in your display. If you don’t see micro bubbles in your display that’s a good sign but it could be that you have something in your sump preventing the micro bubbles for making it to your display. Now let’s look at your sump if you can see that your skimmer is allowing microbubbles to exit the and it is in the section where you want to place your probe this will be an issue. There could be another factor that causes you to have micro bubbles in your sump this could be the return water coming from your display. If you have a Derso drain setup they are notorious for creating bubbles due to the nature of the drain.

How to defeat these blasted things lol....
Well it’s simple stop them darn things, no really stop them.
I would say it’s the return drain or the skimmer causing your bubble issue.

Your drain(s)
If you are using a herbie drain that is tuned to a full siphon and your over flow is not allowing the creation of bubbles from the spillover you won’t have to worry about that being a source. If you have a Derso drain you will need to convert to a herbie or modify Derso so it won’t suck air. The only way I have found to do that is by adding gate valves to the tubbing under the tank and closing it down until it’s backed up with water so it can’t suck air. You may need to adjust your return volume to do this so don’t overflow your tank. Next you could try a series of sponge to block the bubbles and try mesh socks.

Your skimmer
it’s simple if you can see bubbles coming out of the skimmer you will need some kind of bubble trap or mesh bag to catch the bubbles.

Electrical interference
some people say is this really a thing, yes it is. The salinity probe is the one that has the most issues with electrical interference if you have multiple DC power bricks or AC power wires running along the location that your probes are going to be placed and or near the location of your head unit you going to have issues with your probe.
I know that sometimes it seems like it can be an impossible task to revert the probe wire from coming into contact with any of these wires around your system. Well there’s a few things you can do the first thing being buy some wire shielding and place it over the probes cable that way you know that it will be protected. Sometimes it can be as simple as plastic wire looming the solid kind not the spiral kind that you can see the wire through it. The next thing that you can do is if you plan on putting your Apex together in a fancy cabinet and running all the wires through the little holes next to each other make especially sure that you’re still under the probe wire is shielded so it may not come into contact with any power wire and try place your head unit away from your eb832 or eb8.

Let’s say that now you have your probe in the system or you’re getting ready to purchase or install a apex system the following will help you get a better turnout in the end.
So you got your apex and your salinity probe. You are going to have to calibrate it.

You should only have to do this once. Make sure it is dry and you have not put it in the water yet. If you have already put it in water and connected it the disconnect it. Rinse it in ro di water then let dry completely before calibration.It helps to soak the packet of calibration fluid in the sump so that it is the same temperature of your system. Then once that’s done rein it in with temp compensation settings once in system water. You don’t have to soak it if you don’t want to. I didn’t have to soak mine I just calibrated it and then compensated it until it matched up with my atc refratormeter.

I’m going to put probe placement in this section but it goes along with electrical interference.

This is an actual picture of my probe holder in my sump. I have found through my experience that it is good to leave a space in between the salinity probe and any other probe. I do this to prevent any interference from another probe. You may notice I keep my temperature probe off to the side of the probes all together that way I know that I’m not getting any interference. Doing this has worked great for me. I had some fluctuations in the past and then once I did this after battling any of the other issues that I had stated previously I have had a very consistent reading.

So you say to yourself what can possibly be after correcting those few things.
Well there is more and there are a few things we still need to address.

One thing you’ll need to realize is that temperature has a great factor In salinity readings. So now that you have the probe calibrated and it’s in your water and all the other factors have been taken away as stated before that might be an issue your ready for the next step.
Next you will need to use temperature compensation settings in fusion for the probe. You will also need a automatic temperature compensation refractormeter. You need to open up your temperature compensation settings in fusion then take a reading with your refractormeter with a sample of your systems water, you can do this a few times making sure that you’re getting a good reading and then adjust your temperature compensation until it reads the same as your refractormeter. Make sure that your meter does not have any salt buildup from your last reading and is clean before you use it.
You must keep in mind that if your temp fluctuates it will cause your salinity to change throughout the day regardless of no other factors like stated above. Don’t blame the probe if temp goes up and down and salinity is up and down. If you can keep the temp very stable then salinity shouldn’t change much unless ato systems are causing additional fluctuations talked about next.

Now let’s talk about auto top off systems.

Some ATO systems have some discrepancy of when they come on and go off based on precision of sensors sometimes leaving you with readings that are not perfect or completely stable. Some fluctuation is of course normal you will have this there’s no reason to chase small changes in your numbers. You will notice that during evaporation you’re so salinity will rise and once your ATO system adds water it may drop. This is due to it not keeping the water level exactly consistent.

Follow up.....
If none of this helps you get your probe working correctly then you may in fact have a bad probe or hardware related issue. It happens
Another note is that those micro bubbles seem to stick to anything they come into contact with simply turning your probe upside down may help but not guaranteed. Getting ride of the micro bubbles all together is best. Of course you will always get some when you shut the return pump down or start it up but usually all goes away and you’ll be okay.

Make sure to regularly carefully clean all your probes. I use a very soft bristle brush. Be gentle as there is a glass tube inside the salinity probe.

If you’re comparing to a handheld meter that doesn’t have any temperature compensation you’re reading isn’t going to match up with your number on your Apex due to the temperature compensation. I see people saying I put another tester in the water and it’s way off and that is why.

Also if your system is at 78 degrees Fahrenheit and 35ppt then if temp drops to say 76.1 then salinity will read 34.30 ppt so don’t freak out. It’s okay and stable with the temp. If you go and make changes like adding salt to your system when your temperature rise back up you’ll be over so the key to this is keeping your temperature is stable as possible and then you won’t see the fluctuations in your sanity hopefully this makes sense to y’all.

It is always wise to have a good backup test but if your salinity changes because your temperature went off it’s normal stable temp then your salinity number will change and you will also see it in a ATC refractormeter as well. So I suggest that the temp be brought back to the proper temp were the salinity is normally stable and then do your back up checking. That way you aren’t changing perfectly fine water just based of a reading that is at a different temp but is still correct once temp is right again

Hope this helps you out and you enjoyed the read.
Thanks for reading.
Written by or typed lol by
Joseph O’Donnell a.k.a. Joekool
About author
Reef Junkie

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Super helpful and great guide.
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Great. Glad you liked it.
Yes good information.
My salinity probe was all over the place when I started out.
Found another thread about separating the wiring, did that and rock solid readings.
I wound up calibrating my probe to the water column itself after testing with two other pieces of equipment, ATI and Milwakee refractometers. I found this to be a better solution over using the calibration fluid. YMMV.
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This was very helpful is stabilizing my Probe. Thank you!!!
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Hopefully you feel the same. Please rate this article.

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