Who uses it and do you trust it 100%? I just retested my salinity with my old refractometer and with a new meter. One was calibrated with 35ppt and the other with ro/di. Both of them read my salinity at 1.031. I then tested the calibration fluid and it test at 1.021 and I run the tank at 1.026 so needless to say my salinity is off .05 using the probe. I lost a bunch of stuff over the last few months and have tried everything and wondered what was going on. I use BioActif salt and have wondered why I have been having to add more to get me to 1.026 and now I found the reason. The calibration fluid is WAY off its 50mS and that should be 1.024 roughly. So to everyone out there be careful and make sure your solution or the probe is calibrated correctly. I have talked to 2 other profi users that have the probe and both of them tell me they have had problems with there's also. Both of them tell me if there probe reads about 1.02-1.021 they know there tank is around 1.025-1.026. Pretty bummed as I do believe this is the culprit to a loss of a few K in acans one of the easiest corals to keep period. I finally went back to my old trusty 15 yr old refractometer I used on my sps tank for yrs with solid results. Needless to say i will not use this as a standard anymore.
conductivity probe worthless
- Thread starter nanotank
- Start date
AQD_ottawa
New member
Firstly it is not worthless, if that was the case we would have public aquariums around the world relying on them, or sell dozens a month without issue.
So hopefully I can give you some good guidence
1. a refractometer should never ever be calibrated to Ro water it should be calibrated to natural sea water, there are two good products on the market for this, either pinpoints 53ms calibration solution or Fauna marins multi reference solution.
2. when calibrating the GHL probe temperature plays a massive role in this, so ensure the probe and the clibration solution are at the exact same temperature, even half a degree off will give you bad results.
I have covered this in huge depth a few times here and once the proper proceedures are followed nobody has a single issue
Here is how I calibrate mine (I actually use 53ms solution)
put solution in sump for 24 hours
set the calibration to tank temp mode
leave probe in solution for 5 minutes to react
Go through calibration proceedure
After calibration leave probe in solution to check accuracy, if reading as per calibration solution it is calibrated.
If you are using a refractometer calibrated to RO water it WILL be very innacurate that there is no argument and is covered in the multiple threads on RC.
Hope that helps, but happy to guide further are expand further if required
So hopefully I can give you some good guidence
1. a refractometer should never ever be calibrated to Ro water it should be calibrated to natural sea water, there are two good products on the market for this, either pinpoints 53ms calibration solution or Fauna marins multi reference solution.
2. when calibrating the GHL probe temperature plays a massive role in this, so ensure the probe and the clibration solution are at the exact same temperature, even half a degree off will give you bad results.
I have covered this in huge depth a few times here and once the proper proceedures are followed nobody has a single issue
Here is how I calibrate mine (I actually use 53ms solution)
put solution in sump for 24 hours
set the calibration to tank temp mode
leave probe in solution for 5 minutes to react
Go through calibration proceedure
After calibration leave probe in solution to check accuracy, if reading as per calibration solution it is calibrated.
If you are using a refractometer calibrated to RO water it WILL be very innacurate that there is no argument and is covered in the multiple threads on RC.
Hope that helps, but happy to guide further are expand further if required
I used FM 53mS and have since it came out. I have also made my own 35ppt solution from Randies recipe. That's why I used 2 meters 1 with ro/di and 1 with 53mS as I said above to double check and verify my findings. There is def a problem that the 50mS solution is way off which in turn makes the probe useless if profilux calibration solutions r WAY off. Seriously we r talking a HUGE $ loss over salinity and I believe that is the case 1000%. I have been doing this way to long and got caught up in the techie side of the hobby and it has cost me dearly.
AQD_ottawa
New member
I understand, however if you have not followed the temperature compenstion correctly it will read off
The simple test to the solution is to calibrate it correctly with the 50mS and then after calibrating leave it in the solution if it reads 50mS then it is calibrated and accurate, the unit can only read what it is put in.
Follow that up by then putting it in 53ms (assuming this is new and not contaminated) then you can see how it reads, of course making sure the 53ms is the same temp as the 50ms and the probe, otherwise the test is pointless.
Soutions have a shelf life of about 6 months and should not be contaminated.
The 50ms is sold worldwide and there is not one single support case for this solutions innacuracy, it comes from a German lab so we have no real concerns.
Salinity is a difficult subject due to multiple things that can get in the way of cross referencing. I am in the middle of doing a full write up on the process which I hope will help shed light on this.
The simple test to the solution is to calibrate it correctly with the 50mS and then after calibrating leave it in the solution if it reads 50mS then it is calibrated and accurate, the unit can only read what it is put in.
Follow that up by then putting it in 53ms (assuming this is new and not contaminated) then you can see how it reads, of course making sure the 53ms is the same temp as the 50ms and the probe, otherwise the test is pointless.
Soutions have a shelf life of about 6 months and should not be contaminated.
The 50ms is sold worldwide and there is not one single support case for this solutions innacuracy, it comes from a German lab so we have no real concerns.
Salinity is a difficult subject due to multiple things that can get in the way of cross referencing. I am in the middle of doing a full write up on the process which I hope will help shed light on this.
I am currently temp compensating both the 50 and 53mS and I will perform another calibration in a hr or so. I did it like you posted last time and I will do it like that again and report back. How often do these need to be re-calibrated? Mine was done like 5-6 months ago. I felt it was done correctly and read decent when I first did it but feel it has drifted off over the last few months causing all the problems.
AQD_ottawa
New member
Always calibrate monthly, the platinum tip must be wiped also at this time, if you dont do this then you will have innacuracies, just as you dowith any probe.
If you have not calibrated or cleaned for 5-6 months then you will get drift and thats not the fault of the solution.
If you have not calibrated or cleaned for 5-6 months then you will get drift and thats not the fault of the solution.
I can't get it close to reading 50mS or 53mS after about 6 different calibrations. I'm getting 43.7 with 50 and up to 47 with 53. So not sure whats up have manually entered the temp in C with the temp prob in the tank and then moved after cleaning and drying off to the calibration solution then let it sit for 4-5 min to get it to stay constant. Still no dice..
No clue, did it again with the calibration solution submerged in the tank to stay constant at 25.4C with the tank water and with the 53mS it reads 50 after calibration. So now I am wondering if my temp sensor is out of whack ***? This has turned into a PITA. Anybody looking to buy a salinity probe LOL.. I think I will just trust my tride and true refractometer as I am getting know where with this. Any warranty period on these EXPENSIVE probes?
Ok trying one last time with the 50mS submerged in the tank and have verified it matches tank temp with temp probe. Going to keep it in the tank while its calibrating so temp should be PERFECT and we shall see what readings I get. Rem I did this with the FM 53 not long ago. I will order new ref solutions just in case. I really wanna trust this so/so but not having anything positive to make me feel that way currently.
Yep I did Greg 53 reads 35ppt or 1.026 on refrac. That's the reason I started looking into salinity as I have had problems and mixing bioActif from TM for the last couple months it seems on water changes I have had to use more than in the past. It was a new bucket so thought maybe that was the case. Doing this for so long I have become lazy it seems 
AQD_ottawa
New member
Hi
The probe in this case is very dirty.
as you said above the probe had not been touched for 5-6 months, this means you likely have a big build up of crud (not a better word sorry) on the platinum plates.
You will need to really clean these off but carefully, my favourite method is a soft cloth dipped in silver polish very lightly wiped between the plates then rinsed.
The probes are laboratory instruments hense the price, however they still need maintaining regularly to avoid such issues.
The fluid also will take more than a few hours to reach tank temp you can check the status by using the GHL temp probe. But your issue is maintenance, I highly doubt the calibration is the issue here, simply the probe can not read right due to being left dirty for so long.
The probe in this case is very dirty.
as you said above the probe had not been touched for 5-6 months, this means you likely have a big build up of crud (not a better word sorry) on the platinum plates.
You will need to really clean these off but carefully, my favourite method is a soft cloth dipped in silver polish very lightly wiped between the plates then rinsed.
The probes are laboratory instruments hense the price, however they still need maintaining regularly to avoid such issues.
The fluid also will take more than a few hours to reach tank temp you can check the status by using the GHL temp probe. But your issue is maintenance, I highly doubt the calibration is the issue here, simply the probe can not read right due to being left dirty for so long.
AQD_ottawa
New member
yep they will look clean to the naked eye, remember its extremely dificult to see in a slot that is .20mm gap
If cleaning has raised it then you are on a winner and the issue has been found.
Just dont go overboard on the cleaning, if you strip the platinum you have trashed the probe.
If cleaning has raised it then you are on a winner and the issue has been found.
Just dont go overboard on the cleaning, if you strip the platinum you have trashed the probe.
AQD_ottawa
New member
I can not emphysis this enough
1. cleanliness of probe
2. matching calbration temp
Get those two right and you will never have issues. Just keep in mind you are dealing with a sensitve laboratory instrument, the price of the probe is not to keep me in shorts, you are paying for probably one of the highest grade probes on the market, so it needs equal treating with care and attention.
I hope that does not come across as me preaching, thats not what I am trying to get across. Just these expensive items are not normally available off the self and are used within lab establishments, so the same kind of attention given there has to be carried forward here.
All they need is once a month rinsing and wiping, do it the same time as you would all other probes, part of the maintenance cycle and you should never have issues.
1. cleanliness of probe
2. matching calbration temp
Get those two right and you will never have issues. Just keep in mind you are dealing with a sensitve laboratory instrument, the price of the probe is not to keep me in shorts, you are paying for probably one of the highest grade probes on the market, so it needs equal treating with care and attention.
I hope that does not come across as me preaching, thats not what I am trying to get across. Just these expensive items are not normally available off the self and are used within lab establishments, so the same kind of attention given there has to be carried forward here.
All they need is once a month rinsing and wiping, do it the same time as you would all other probes, part of the maintenance cycle and you should never have issues.
AQD_ottawa
New member
I think you are not giving it enough time.
Leave the bottle of solution in the sump (making sure no sump water can get into the botle) for 24 hours
Come back tomorrow, put the tank temp probe in the solution (make sure tank temp probe is clean and dry first) take the reading after 5 minutes.
Then go from there.
If you scrub that probe too much you will kill it please be careful
Leave the bottle of solution in the sump (making sure no sump water can get into the botle) for 24 hours
Come back tomorrow, put the tank temp probe in the solution (make sure tank temp probe is clean and dry first) take the reading after 5 minutes.
Then go from there.
If you scrub that probe too much you will kill it please be careful
