What could cause this drop in salinity!!?

[TangingOut]

OP, you're telling us that you didn't immediately verify with a refractometer? I suppose unless you don't own one, but it would have been the first thing I did if I was in your situation.

 

[ReeferMadness80G]

OP, you're telling us that you didn't immediately verify with a refractometer? I suppose unless you don't own one, but it would have been the first thing I did if I was in your situation.

No, I didn’t check with my refractometer. Lol it seems funny that I didn’t now that you say that! I guess I’m leaning on my apex a little too much! I’ve never been able to monitor my salinity like I can with the Apex so I was more concerned if swings like this were normal. With the Apex it’s like going from taking a picture of your salinity vs watching a live streaming video of it. I also need to calibrate my refractometer so I can use it as a fail safe. Thanks TanginOut I guess I wasn’t thinking!

 

[TangingOut]

I purposely chose to not monitor my salinity with apex after seeing so many having issues accuracy and probe drift.

 

[ReeferMadness80G]

I purposely chose to not monitor my salinity with apex after seeing so many having issues accuracy and probe drift.

Seems to be ok now! I forget redundancy is key in this hobby! I’ll make sure to double check every once in a while now.

 

[lbacha]

I had the same issue happen twice to me and both times it was from the ATO return creating an air bubble that got into the probe and throwing it off. My sump is small so I had my probes in my return chamber. Now that the probe is no where near air bubbles it has worked fine. I have noticed it isn't dead on 35ppt so I use it more to watch for spikes or drops in salinity. If it goes up I know my ato has run dry. It also caught when I rearranged my ATO return line and put it below the level of the water level on my ATO container. I ended up siphoning and extra gallon of water into the tank which the apex caught.

That being said I check salinity once a week when I check calcium just to make sure the probe is correct. I also do a quick PH test to see if the ph probe is drifting and a temp check about once every 2 weeks.

 

[saltyhog]

Interesting discussion. How important is monitoring salinity/how often should we? In the last 5 years I've only found my salinity not to be 35ppt one time (36ppt that time).

What are ways our salinity can vary? The only ones I could come up with were 1) water change salt mix not accurate, 2) Top off water accidently replaced with salt water, 3) large amounts of 2 part dosing, 4) excessive salt creep, 5) ATO malfunction...though that would be obvious as water levels in the tank would change.

What else is there to go wrong that would cause salinity to change?

 

[Randy Holmes-Farley Verified Community Expert]

Interesting discussion. How important is monitoring salinity/how often should we? In the last 5 years I've only found my salinity not to be 35ppt one time (36ppt that time).

What are ways our salinity can vary? The only ones I could come up with were 1) water change salt mix not accurate, 2) Top off water accidently replaced with salt water, 3) large amounts of 2 part dosing, 4) excessive salt creep, 5) ATO malfunction...though that would be obvious as water levels in the tank would change.

What else is there to go wrong that would cause salinity to change?

I monitored it frequently and did adjust it many times.

As to your question of other causes (all of which I have had happen)...

ATO replacing water that was spilling out/leaking somewhere,
A rising water level in the aquarium somewhere besides where the ATO senses (like a refugium due to a partially blocked drain pipe)
Automatic water changes messes up (say, runs out of new salt water, or one of the in/out pumps fail)

 

[don_chuwish]

Skimming removes salt water, which then is replaced with top off water too. But it's rarely a large enough amount to matter.

 

[Ace6090]

I had the saw issues you saw as well as may others. I found the following to help:

1) Keep the probe on an angle, sensor end up cords down, 22-45 degrees. This helps air bubbles stay off the sensor.

2) Have a powerhead or something near the probe to keep water circulating but not blowing directly on the probe

3) Calibrate with a fresh mix of salt water which you measured as accurately as possible and verified with a refractometer. I found when using the calibration solutions the probe reads correct in them but then not when put back in the tank

4) Automated readings are only for monitoring, always check manually BEFORE making any vast changes. This goes for pH, salinity, ORP (I personally never check) and so on. I have seen too many strange readings from perfectly calibrated probes and been a victim of quick reactions. Manually testing usually won't add enough time to make a significant difference

 

[lbacha]

So to add to calibration I just got a bottle of brightwell refractometer calibration liquid (35ppm solution) and tested my refractometer and found it was off by 2 ppm. After calibrating i found out that my salinity was 33ppm. Prior to this I was using distilled water to calibrate to 0 (it always read 0 so never had to calibrate actually). After calibrating distilled water still showed as 0 ppm so it seems that distilled water isn't the best for calibrating

 

[bhavy]

Air bubbles stuck in probe

 

[bhavy]

I usually hang my probes within a 4" media bag in the sump. I kept getting air bubbles or other things causing my probes to read wrong. I would try that....

 

[Mindi]

been there, done this, with export of skimmate to back yard.( out of sight) Skimmer went into overdrive for a couple of days for another reason and I exported a heap of saltwater which the ATO replaced with fresh.

 

[ReeferMadness80G]

So now my Salinity is 37.5 and setting off alarms what the heck

 

[ReeferMadness80G]

So now my Salinity is 37.5 and setting off alarms what the heck

However I’ve checked with my refractometer and it’s showing 35ppt, now let’s hope my refractometer is correct. I have no calibration fluid.

 

[User1]

But bear in mind you cannot swap a 4 electrode cell into a meter designed for a 2 electron cell.

You must be a mind reader too - I was just going to reply to an earlier post in this thread about the 4 electrode probe and if it is compatible with Apex systems...

 

[Forsaken77]

I don't have an Apex, but I know a lot of people don't even use the salinity probe because it jumps around so much. It's more accurate to just test it.

 

[lbacha]

So now my Salinity is 37.5 and setting off alarms what the heck

Yeah I turned the alarms off I really recommend that lol. The salinity probe can get a little crazy lol

 

[dgrigor02]

I don't depend on the conductity. This is one of the things I was disappointed with, I thought I would be able to depend on it more than I can.

It seems pretty sensative to interference. I have never been comfortable enough with it to depend on it for anything just monitor.

When looks out of whack, I confirm with refractometer then recalibrate with the tank water so that they match. I just got more frustrated trying to use the salinity packets and it be off from my tank readings. While it may not be 100% accurate ( if your refractometer is off ) at least it will help monitor variations.

 

[Randy Holmes-Farley Verified Community Expert]

I don't depend on the conductity. This is one of the things I was disappointed with, I thought I would be able to depend on it more than I can.

It seems pretty sensative to interference. I have never been comfortable enough with it to depend on it for anything just monitor.

When looks out of whack, I confirm with refractometer then recalibrate with the tank water so that they match. I just got more frustrated trying to use the salinity packets and it be off from my tank readings. While it may not be 100% accurate ( if your refractometer is off ) at least it will help monitor variations.

IMO, this is an issue of the controllers, not the method. Maybe also partly leaving the probe in 24/7, which I never recommend. I've used it without such issues for decades in many contexts, both reefing and chemistry lab.