Apex shows a steady climb in salinity - why?

[gardiendepoisson]

I have two different, calibrated refractometers. The water change puts .025 water in automatically (AWC that's turned off until I figure this out). The ATO works perfectly; when I bail saltwater out of the sump, it kicks in at the right time to add RO from the reservoir. Despite this, for the last month or so, I watch a steady climb in salinity that's a perfect upward ramp. How can this be? The refractometers are reading .030 right now despite the Apex value which translates to around .026 if I'm doing my math right. I'm stumped. The drop you see is from bailing out saltwater and adding RO. I also did that a few days ago and watched the ramp go right up. What in the world is going on?

 

[TokenReefer]

Are you dosing anything?

 

[MikeCHI]

Barring the easy answer (topping off with salt water) thats a tougher one.

One of my biggest gripes is the inaccuracy of testing equipment. Even with myhigher end stuff like Apex, Seneye, Trident, I get horribly conflicting information constantly and still have to take an average of 3 or more testing types. Very frustrating.

So it could be a bad probe maybe? I would mix a batch of salt water in a bucket with a heater and put your probe in that and see if it keeps creeping up in the bucket. That should tell you if its the probe or something in the aquarium..

 

[gardiendepoisson]

Are you dosing anything?

No.

 

[gardiendepoisson]

Barring the easy answer (topping off with salt water) thats a tougher one.

One of my biggest gripes is the inaccuracy of testing equipment. Even with myhigher end stuff like Apex, Seneye, Trident, I get horribly conflicting information constantly and still have to take an average of 3 or more testing types. Very frustrating.

So it could be a bad probe maybe? I would mix a batch of salt water in a bucket with a heater and put your probe in that and see if it keeps creeping up in the bucket. That should tell you if its the probe or something in the aquarium..

The only thing is, my salinity is definitely high according to the two refractometers. So it looks like it's creeping up and it's not just the probe.

 

[MikeCHI]

without dosing anything its really tough to see a gain of that much salinity in a 180 gallon tank from like some rock or something. If you think of the actual volume of salt you would need to add to that much water to make a measurable difference.

Sorry, maybe someone else has an idea. I'm still hung up on the testing process. Maybe recalibrate the refractometers. Maybe give some more info on what's in your tank? Although barring dosing or temperature changes I cant see anything coming close to adding that much salt.....

 

[TokenReefer]

Verify the awc pulls the same amount it puts in? If the readings are to be trusted the salt has to be coming from somewhere...

 

[MikeCHI]

Verify the awc pulls the same amount it puts in? If the readings are to be trusted the salt has to be coming from somewhere...

Yeah you could try that too. Maybe switching to manually refilling RO in the tank and see if the graph looks more like a flat wave

 

[gardiendepoisson]

Barring the easy answer (topping off with salt water) thats a tougher one.

One of my biggest gripes is the inaccuracy of testing equipment. Even with myhigher end stuff like Apex, Seneye, Trident, I get horribly conflicting information constantly and still have to take an average of 3 or more testing types. Very frustrating.

So it could be a bad probe maybe? I would mix a batch of salt water in a bucket with a heater and put your probe in that and see if it keeps creeping up in the bucket. That should tell you if its the probe or something in the aquarium..

Thanks for the idea. I'll give it a shot. It still looks like the salinity is actually creeping up though, according to the refractometers.

Verify the awc pulls the same amount it puts in? If the readings are to be trusted the salt has to be coming from somewhere...

I turned off the AWC the other day in order to try to get a handle on this. There's nothing going into the tank except RO topoff.

 

[TokenReefer]

From my perspective I'd look at the things that are putting salt into the system. The awc is all I can see from here

 

[gardiendepoisson]

Update: I found a spot in the cabinet with a lot of accumulated salt that may have been dripping little bombs into the return chamber right next to the salinity monitor. I think it was throwing off the reading without affecting the tank much, considering the water volume. Now that I've gotten rid of it, the reading has leveled off. My bad for not catching it earlier.