Where is my salt going?

[sg88]

I hope this is a good forum for this question:

I am setting up a new aquarium as a relative newbie to marine aquariums and complete newbie to sump-based systems.

I have started to cycle my aquarium with Dr. Tim's One and Only and Ammonium Chloride. 5 days into the process only slight drop in the cycle numbers, but what is interesting to me is that my salinity is falling rather than rising. I am awaiting my ATO reservoir in the mail, so I am topping off my sump by hand each day using about 1/2 gallon of water. However, because my salinity started low and my Apex, which was calibrated successfully, shows a downward trend, I am topping off with seawater rather than pure RO/DI water as I would expect that I need. I do not see any salt buildup on the tank, in the overflow or and around the sump, yet the number slowly falls.

Any ideas why this might be?

I attached an image of my Apex salinity probe tracing since I started the probe a day or 2 after I first put salt water in the system. The beginning number at just about 35 ppt (1.026) was the probe in the calibration solution. then it was 28.8 (1.022) when I put the probe in the sump and has slowly been drifting down since. The seawater that I use in my tank is 1.027. I assume that the difference from the start was a dilution effect of remaining RO/DI pure water from my leak test after I drained the tank and sump. I am guessing that I had pure water in the lines to the chiller and UV sterilizer that did not drain back into the sump and there was an inch or so of water in the sump which would be close to a gallon out of total volume of about 50 gallons.

 

[92Miata]

Have you checked the salinity with something other than the Apex?

 

[SMSREEF]

That just can’t be right...
I would get a different test for salinity. You could also take some in to your LFS to test for you.

 

[Sisterlimonpot]

It's because it doesn't test salinity, it tests conductivity in the water. There are many factors that can make the levels drop. Do some research to some pitfalls of a conductivity probe compared to salinity.

 

[phatduckk]

I’d recommend you double check with a refractometer as well.

When I’ve wanted to raise salinity I’ll just let water evaporate until it gets where I want it. Then you can tip off with salt water all in one shot. same concept, just less work.

 

[sg88]

Have you checked the salinity with something other than the Apex?

Thank you, I just did...Apex 27.6 (1.021) and Hanna Salinity Checker 31.867 (1.024). So clearly an issue with the apex probe. I will re-calibrate, but wonder if I need to check with Neptune Systems about a new probe.

 

[sg88]

I’d recommend you double check with a refractometer as well.

When I’ve wanted to raise salinity I’ll just let water evaporate until it gets where I want it. Then you can tip off with salt water all in one shot. same concept, just less work.

...and that was my thought but just confused to see the number continuing to drift downward despite the saltwater top-offs. But as 92Miata questioned a confirmatory test and my Hanna Checker showed a higher level of salinity as I note above.

 

[Cory]

If there isnt a leak in your tank, there isn't ANY reason for salinity to drop.

 

[Luke’s reef]

Unless you have a leak or a massive amount of salt creep some where in you tank You would never see the SG drop like that under normal circumstances. Id say continue to test using the hanna checker and possibly another method to double check your results, and as to the adjustments I would change it naturally using the evaporation method or when you do your next water change simply mix it one or two points higher. Keep us updated on whats happening and hope you get it sorted.

 

[DSEKULA]

Are you running a skimmer and ato?
A wet skim with ato would have the potential to show that drift. Also apex conductivity probes arnt that accurate for salinity ime.

 

[Erick Armanii]

The apex probe is garbage and doesn’t accurately read anything other that temp lol..

I thought the same thing when I first connected mine. For a while I was running around 37.7ppt after some sump cleaning and wire management the probe reads a little lower but no where near 1.026.

Any air bubble or electrical interference will get the numbers out of line..

 

[DSEKULA]

I have two probs on the same tank ones in the dt the other in the basement sump. Im lucky if they run similar readings like they are now... They don't even trend (rise and fall) at the same times . Don't go by these probes to make adjustments just use it as a general guide for when to check with a more accurate meter.

 

[sg88]

Are you running a skimmer and ato?
A wet skim with ato would have the potential to show that drift. Also apex conductivity probes arnt that accurate for salinity ime.

No, just circulating seawater as the tank cycles “fishless”.

 

[jda]

Salt Creep and emptying skimmer cups will lower salinity as you replace with fresh top-off water. This happens slowly, though.

 

[Tamberav]

Thank you, I just did...Apex 27.6 (1.021) and Hanna Salinity Checker 31.867 (1.024). So clearly an issue with the apex probe. I will re-calibrate, but wonder if I need to check with Neptune Systems about a new probe.

the salinity probes are known to have issues. It is great if they send you a new one but don't expect it to fix the problem long term. Any other wires near them can interfere with the reading too, even other probes. I don't even bother to look what mine says anymore.

 

[jda]

Don't trust any probe without real verification. They can be Ok for a while, but they all drift and get unreliable. This goes for pH and every other one. A real lab grade salinity or pH probe is well over $1000 and what is sold in this hobby is almost garbage. Using them as a guide is cool, but always have something more reliable on hand to check them. Also, never have your controller perform an action based on the results of any probe... just alert.

 

[Dj City]

Apex salinity probe rises and falls with temp.
Look at your graphs and you should see.

 

[Darren in Tacoma]

In the industry I'm in we use probes to monitor conductivity in water and it is very common to get incorrect readings if the probe wire is ran adjacent to a power wire.

 

[sg88]

Unless you have a leak or a massive amount of salt creep some where in you tank You would never see the SG drop like that under normal circumstances. Id say continue to test using the hanna checker and possibly another method to double check your results, and as to the adjustments I would change it naturally using the evaporation method or when you do your next water change simply mix it one or two points higher. Keep us updated on whats happening and hope you get it sorted.

I don’t mix saltwater, I use fresh seawater from a tap that pulls water off-shore and is the same water used but our local aquarium (Waikiki Aquarium). Used a refractometer yesterday and found the SG Of the seawater to be 1.024 while my tank is at 1.022. So as I add seawater to top off rather than pure water that should slowly come up. Sounds like I have some me troubleshooting regarding bubbles, maybe overlying wiring etc. I have no leaks that I can see or feel and I have Apex leak detectors behind the sump and on the floor behind the cabinet.

 

[sg88]

In the industry I'm in we use probes to monitor conductivity in water and it is very common to get incorrect readings if the probe wire is ran adjacent to a power wire.

Thx, I have that now on my troubleshooting list when I get home from work today.