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Old 08/06/2018, 07:32 PM   #1
Cowlesdc
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Salinity testing question

I am having an issue trusting my testing for salinity on my tank. It has been up and running for 8 months with several healthy fish and corals, and I have not had any issues with any livestock what so ever, knock on wood.

My issues is that my Apex and my ATC refractometer readings are way different and I dont know who to trust.

I tested this evening and here were my results.

Apex 34.8 ppm
ATC calibrated with RO water - 32ish ppm
ATC Calibrated with 35ppm fluid - 30 ppm

Any advise?


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Old 08/06/2018, 11:25 PM   #2
bertoni
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I wouldn't trust anything calibrated with RO water. I might invest in a a second calibration solution, or make one:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

How was the Apex calibrated? With the 35 ppm fluid? What brand is the fluid?


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Old 08/07/2018, 10:25 AM   #3
Cowlesdc
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The solution is from Aqua Craft Products.

I calibrated the Apex with the fluid it came with.

I am going to get a LFS to test tonight, as well as buy new calibration fluid for the apex.

I am also seeing random swings from the apex of .5ppm. For example, F, Sat, Sun of last week it was steady at between 34.7 and 35. Then M, T, and W at noon each day it dropped to 34.4 or 34.5 and then steadily rebounded. Then Th - Yesterday steady in the 34.7-35 range.

Thanks for the help.


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Old 08/07/2018, 02:51 PM   #4
hkgar
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//you need to calibrate your refractometer with 35 calibration fluid and than trust that. I have a Apex and the salinity probe. I monitor it to catch any swings but trust my refracometer to see what my salinity is.

Do not calibrate to 0 ro water.


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180 gallon, 40 gallon sump, 8 ATI T5's, MTC MVX 36 Skimmer, Apex controller Reef Octopus CaRx

Current Tank Info: 2 Barred Rabbitfish, Red Head, Yellow/Purple, Hoevans, Possum, 2 Leopard Wrasses, Kole, Purple & Atlantic Blue Tangs, Matted Filefish, 2 Percula Clown, 4 PJ Cardinals, Swallowtail Angel
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Old 08/07/2018, 11:40 PM   #5
bertoni
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The Aqua Craft product is advertised as working for refractometers. Is there some reference from them that indicates it'll work with salinity meters (conductivity probes)? If not, I'd try the PinPoint 53 mS solution.


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Old 08/11/2018, 09:55 AM   #6
thegrun
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I get too many swings in my conductivity probe to trust it. They are susceptible to electronic interference and prone to small swings.


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Old 08/28/2018, 04:54 PM   #7
Cowlesdc
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Update

So I took my Refracto and some tank water to my LFS and checked everything against their stuff. I think my refracto has been dropped one to many times. I would test the same water multiple times on both refractos and mine would change but the stores stayed consistent. My best guess is that the actual scale is some how no longer firmly in place and is moving around. If I am very careful with it I can calibrate it and then immediately get a reading, but even setting it down on a table throws it off a little. So, I ordered a new one and more calibration fluid for my probe. They still dont match but they are close enough for me.

Thanks for all the help


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Old 08/28/2018, 07:10 PM   #8
bertoni
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Well, I'm sorry to hear that the refractometer is broken, but that does explain a lot. I hope your new one works better!


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