I wish i didn't calibrate...sort of!

[BoSalman]

So, I got tired of looking at my record high salinity readings on apex (due to error in calibration) and decided to get it properly calibrated and put it in use...

I purchased a pinpoint calibration solution and waited eagerly for it to arrive. I have "hopefully" calibrated the probe the right way this time and i was shocked! I know that probes may be off due to many factors, but it rang an alarm to me..

Refractometers sold locally here are cheaply made ones, and their calibration is not done right! they use RODI (or even tap) to calibrate them, and no one that i know of uses standard solutions to calibrate theirs either, and they advise us to use RODI to calibrate... (most LFS here promotes bad practice, you name it, especially in saltwater)

Anyways, I used the same solution (pinpoint) to calibrate my refractometer and it gave me the exact same reading on Apex. Concluding that I am and have been maintaining my reef salinity at 28.5-29 (~1.021 +/-).

When i try to measure my RODI it won't be zero after calibrating with pinpoint.

So I'm now trying to somehow verify which route to go. I have been measuring low Alk/Ca/Mg of the salt mix i use (i know why now!) and I'm wondering if i should stick with the pinpoint calibration point and raise my salinity slowly via ATO up to 34-35 (1.025-1.026 range)?

OR should i hold and try and get a different refractometer (have to ship it over-seas) and hope that it would arrive here in one piece to calibrate it and re-measure?

I'm not trying to make things PERFECT, but knowing that my salinity is off, made me hold all my dosing/WC/...etc schedules to verify that I'm mixing the right amount of salt to begin with!

Below is a screenshot of the probe after calibration, you can see how it was reading in the upper 40s range and the calibration point after..

What would you do in this situation?

 

[SPR1968]

I can only tell you what I do with the Apex salinity probe, as if I use the calibration fluid the probe is way off for whatever reason.

You do need to get a good refractometer that you trust, I use and trust the Red Sea, although it’s very sensitive and needs a quick calibration before each use, I use RODI for that. I also have 35ppm calibration fluid but it comes out the same. I find this refractometer is especially sensitive to temperature so I leave the fluid/saltwater for 10 seconds or so before reading it.

When I am happy that the tank is at 35ppm salinity with my trusty refractometer (on the basis everything is thriving so it’s good!) I calibrate the Apex probe with the ‘manual’ procedure rather than automatic. Just follow this, but when it says dip in the solution, just put the probe back in place in the tank and continue the calibration. Leave it 5 minutes to settle and then finish the calibration

This works every time for me, and the Apex matches my refractometer so I’m happy to trust the Apex readings. I do find the probe needs cleaning every 3 months usually when I get an alert on holiday saying the salinity is 54!

 

[BoSalman]

I can only tell you what I do with the Apex salinity probe, as if I use the calibration fluid the probe is way off for whatever reason.

You do need to get a good refractometer that you trust, I use and trust the Red Sea, although it’s very sensitive and needs a quick calibration before each use, I use RODI for that. I also have 35ppm calibration fluid but it comes out the same. I find this refractometer is especially sensitive to temperature so I leave the fluid/saltwater for 10 seconds or so before reading it.

When I am happy that the tank is at 35ppm salinity with my trusty refractometer (on the basis everything is thriving so it’s good!) I calibrate the Apex probe with the ‘manual’ procedure rather than automatic. Just follow this, but when it says dip in the solution, just put the probe back in place in the tank and continue the calibration. Leave it 5 minutes to settle and then finish the calibration

This works every time for me, and the Apex matches my refractometer so I’m happy to trust the Apex readings. I do find the probe needs cleaning every 3 months usually when I get an alert on holiday saying the salinity is 54!

it's true with the probe being off , it has many factors and this is why i didn't rely on the probe since starting the unit i have. However, it is a huge debate wither to use RODI to calibrate or using a standard 53ms solution. this is where I'm confused/suspecious the most. I looked up the RedSea yesterday and i do rely on their products, just not sure if i would get a refractometer that requires calibration on each test..

With my current ATC refractometer, If i do calibrate (or zero) with RODI, i do test my tank to be 1.025 spot on. But once i use the standard solution I'm down to 1.021.. which is low for my target...

my livestock looks healthy so far, but since I'm planning to dose to maintain certain levels as I'm increasing my stock slowly, I'm now worried about my salt mixing ratio suspecting that my salinity is off after those tests and thus throwing Alk/Ca/Mg off as well..

 

[SPR1968]

The calibration takes just seconds and then you know it’s accurate for each use. RODI/35ppm on, leave 10 seconds and adjust. Done. I also have the DD refractometer but couldn’t read the scale properly (eyes!)

You can use whichever solution you prefer, I’ve just found that with RODI or calibration fluid there is no noticeable difference. I have both so whichever you prefer.

I just find whenever I use the 53ms solution for the probe Apex is out big time.

You just need to trust one of them and I personally wouldn’t trust a computer that’s gives me false readings every 3 months or so. I trust Apex to a point but only when it’s been calibrated to what I trust and that’s my refractometer.

And I have a thriving coral reef so I know it works

As you start or continue dosing and testing the readings you’ll find the correct levels etc., but you just need to find the procedure you prefer to calibrate otherwise you will drive yourself mad lol.

 

[BoSalman]

The calibration takes just seconds and then you know it’s accurate for each use. RODI/35ppm on, leave 10 seconds and adjust. Done. I also have the DD refractometer but couldn’t read the scale properly (eyes!)

You can use whichever solution you prefer, I’ve just found that with RODI or calibration fluid there is no noticeable difference. I have both so whichever you prefer.

I just find whenever I use the 53ms solution for the probe Apex is out big time.

You just need to trust one of them and I personally wouldn’t trust a computer that’s gives me false readings every 3 months or so. I trust Apex to a point but only when it’s been calibrated to what I trust and that’s my refractometer.

And I have a thriving coral reef so I know it works

As you start or continue dosing and testing the readings you’ll find the correct levels etc., but you just need to find the procedure you prefer to calibrate otherwise you will drive yourself mad lol.

That's exactly what i'm trying to do, once am confident with the refractometer i'm going to build on that...

Trying to get this perfectly right isn't gonna happen anyways, so hopefully i can somehow verify my readings...;Bookworm

 

[ColoradoBill]

Glad to hear that others are having the same issue with the Apex salt probe. I've calibrated it 3 times now in the last 7 days and it's jumping all over the board. It would read correctly, between 34-35, for a few days, then suddenly increase to 45. I'd re-calibrate it and then it would read the tank at 25. I've tried isolating the cables away from any potential electrical interference with no luck in increasing the accuracy. It's getting to the point that I just don't trust any reading it gives me.

Anyone else had luck getting these to work?

 

[mbmax]

I love apex but the salinity probe is not good at all . They stop working properly in just a few months, at least in my case.

 

[ZoWhat]

Find 2-3 LFS...start comparing their readings to yours

adjust SG via smaller WCs ever other day. honestly a 5SG push higher in s single day prob not going to present problems BUT I dont know what you have in fish/coral



.

 

[CindyKz]

S

Anyways, I used the same solution (pinpoint) to calibrate my refractometer and it gave me the exact same reading on Apex. Concluding that I am and have been maintaining my reef salinity at 28.5-29 (~1.021 +/-).

When i try to measure my RODI it won't be zero after calibrating with pinpoint. View attachment 857148

I can't find an exact reference for this, but I don't think conductivity standards and calibration fluid are interchangeable, as they measure different things. ETA: I read in one thread that it could depend on the brand and what they are making the solution with.

I would buy or make a refractometer calibration fluid, calibrate using that, and go from there. My salinity probe and refractometer are usually a little off from each other - again, measuring things a little differently. They are within a tolerable range. Randy has written a ton of articles about this stuff.

 

[Mortie31]

I can't find an exact reference for this, but I don't think conductivity standards and calibration fluid are interchangeable, as they measure different things

Spot on, one is to calibrate conductivity the other density, so not interchangeable, unless they are a dual calibration fluid

 

[CindyKz]

According to BRS

Spot on, one is to calibrate conductivity the other density, so not interchangeable, unless they are a dual calibration fluid

According to BRS, the pinpoint solution is a dual calibration though, if the OP is using this one it should work I guess. I have never tried.

ttps://www.bulkreefsupply.com/pinpoint-salinity-calibration-fluid.html