Salinity testing question

Cowlesdc · 08/06/2018, 06:32 PM

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?

bertoni · 08/06/2018, 10:25 PM

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?

Cowlesdc · 08/07/2018, 09:25 AM

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.

hkgar · 08/07/2018, 01:51 PM

//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.

bertoni · 08/07/2018, 10:40 PM

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.

thegrun · 08/11/2018, 08:55 AM

I get too many swings in my conductivity probe to trust it. They are susceptible to electronic interference and prone to small swings.

Cowlesdc · 08/28/2018, 03:54 PM

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

bertoni · 08/28/2018, 06:10 PM

Well, I'm sorry to hear that the refractometer is broken, but that does explain a lot. I hope your new one works better!

08/06/2018, 06:32 PM	#1
Cowlesdc Registered Member Join Date: Jul 2013 Posts: 35	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?

08/06/2018, 10:25 PM	#2
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	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? __________________ Jonathan Bertoni

08/07/2018, 01:51 PM	#4
hkgar Registered Member Join Date: Oct 2002 Location: Dewitt MI Posts: 5,051	//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. __________________ Gary 180 gallon, 40 gallon sump, 3 250 W MH + 4 80W ATI T5's, MTC MVX 36 Skimmer, Apex controller Aquamaxx T-3 CaRx Current Tank Info: A 2 Barred Rabbitfish, Red Head Salon, Yellow/Purple, McMaster Fairy, Possum, 2 Leopard Wrasses, Kole, & Atlantic Blue Tangs, 2 Percula Clown, 3 PJ and 1 Banggai Cardinalfish , Swallowtail, Bellus and Coral Beauty Angels

08/07/2018, 10:40 PM	#5
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	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. __________________ Jonathan Bertoni

08/28/2018, 06:10 PM	#8
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	Well, I'm sorry to hear that the refractometer is broken, but that does explain a lot. I hope your new one works better! __________________ Jonathan Bertoni

08/07/2018, 09:25 AM	#3
Cowlesdc Registered Member Join Date: Jul 2013 Posts: 35	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.

08/11/2018, 08:55 AM	#6
thegrun Registered Member Join Date: Dec 2008 Location: Garden Grove, Ca Posts: 17,023	I get too many swings in my conductivity probe to trust it. They are susceptible to electronic interference and prone to small swings.

08/28/2018, 03:54 PM	#7
Cowlesdc Registered Member Join Date: Jul 2013 Posts: 35	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