Keeping accurate testing results

[davidwillis]

I have an apex with a Trident. However I am questioning the accuracy of the readings for ph, alk, ca, and mg. About 6 months ago I purchased two new ph probes (two different brands). After calibrating both of them, they started to deviate. I figured it may just be because they were new. About a month ago I recalibrated them again, but again they are deviating from each other. One currently reads 7.94, while the other reads 7.82

I am also using a trident, but just yesterday I decided to confirm with my other test kits.
Ca
trident: 477
salifert 300

Alk
Trident: 7.98
salifert: 8.4

I didn't test mag.

After that, I tested a calibration bottle of
alk 8.3
ca 440
mag 1345

Results
alk 8.24. -1% off
ca 507. 15% off
mag. 1300. 3% off

So my question is, is there some good test kits to test ph, alk, ca. I am not sure I trust any of my tests at this point.

 

[CasperOe]

A test kit is only as good as the user, and all of them have some error to take into consideration.

In my mind, it has less to do with accuracy and more with consistency. The best test kit is the one that gives you similar results if you perform it three times in a row.

I am running a Trident too. Do i trust it? Well no, but for me it is fairly consistent.

I use below test kits, as they seem to give me consistent results:

pH - Hanna
Alk - Hanna
Ca - Red Sea
Mag - Red Sea
Phosphorus - Hanna
Nitrate - Hanna

 

[davidwillis]

A test kit is only as good as the user, and all of them have some error to take into consideration.

In my mind, it has less to do with accuracy and more with consistency. The best test kit is the one that gives you similar results if you perform it three times in a row.

I am running a Trident too. Do i trust it? Well no, but for me it is fairly consistent.

I use below test kits, as they seem to give me consistent results:

pH - Hanna
Alk - Hanna
Ca - Red Sea
Mag - Red Sea
Phosphorus - Hanna
Nitrate - Hanna

My biggest concern it the Trident giving me a ca of 477, but salifert 300. I tested both 3 times, and they were giving me very consistent result, but also very different. If it is really 300, then my calcium is extremely low. My guess it is probably just over 400, and my trident is giving me a high reading while my salifert is giving a low reading. I checked the expiration date on the salifert, and it still has a couple years left... I guess I need a third test kit to help settle it.

 

[CasperOe]

I personally never managed to test anything correctly with a Salifert test kit but that is just me!

Remember- it is not just about being consistent; it is about doing it correct consistently Are you sure you're using your Salifert test kit correctly?

 

[Rusty_L_Shackleford]

A test kit is only as good as the user, and all of them have some error to take into consideration.

In my mind, it has less to do with accuracy and more with consistency. The best test kit is the one that gives you similar results if you perform it three times in a row.

I am running a Trident too. Do i trust it? Well no, but for me it is fairly consistent.

I use below test kits, as they seem to give me consistent results:

pH - Hanna
Alk - Hanna
Ca - Red Sea
Mag - Red Sea
Phosphorus - Hanna
Nitrate - Hanna

Bingo. Consistency and stability is more important than actual numbers. It doesn't ultimately matter if your calcium is 420 vs 440, as long as it's consistent.

 

[CasperOe]

Bingo. Consistency and stability is more important than actual numbers. It doesn't ultimately matter if your calcium is 420 vs 440, as long as it's consistent.

Exactly! And how do you even verify that whatever result you get is correct? I don't reckon any of us have lab-grade equipment at home as a control!

 

[jda]

You are just going to have to pick something as your baseline - Segal's Law is real in the world of reefing and cheap test kits. Even the Trident is a cheap test kit wrapped up into a robot.

I would never trust the trident. I trust salifert to calcium and alk, handheld pH pen for pH and Hannah Ultra Low for phosphorous. I don' test for much else.

Why do I choose these? Salifert tests freshly mixed IO perfectly based on the published parameters. pH pen does not drift and stays calibrated if I wash it off every time. Hannah matches up to a more expensive Hach test kit that I cannot afford to replace (got one in a box of free stuff from somebody leaving the hobby once).

Find your truth, or should I say faith? Yours will be different than other people's.

 

[Rusty_L_Shackleford]

Exactly! And how do you even verify that whatever result you get is correct? I don't reckon any of us have lab-grade equipment at home as a control!

I test regularly and my tank is pretty stabile so I know what to expect. If I get a weird result then my first step is retest. A lot of the time it's because I screwed up the test somehow. I also periodically take a sample to my lfs to have them test just to verify my results. Good way to identify a bad test kit.

 

[EeyoreIsMySpiritAnimal]

After that, I tested a calibration bottle of
alk 8.3
ca 440
mag 1345

Results
alk 8.24. -1% off
ca 507. 15% off
mag. 1300. 3% off

I don't own a Trident so forgive me if this is a dumb question... Can you use the calibration solutions to check your Salifert values?

 

[davidwillis]

Bingo. Consistency and stability is more important than actual numbers. It doesn't ultimately matter if your calcium is 420 vs 440, as long as it's consistent.

But 300 vs 470 does

 

[EeyoreIsMySpiritAnimal]

But 300 vs 470 does

What does your salt say it mixes to? How do those numbers compare with the results when you use both tests on fresh saltwater?

 

[davidwillis]

I don't own a Trident so forgive me if this is a dumb question... Can you use the calibration solutions to check your Salifert values?

I'm not sure, that is one reason why I posted on here. Hopefully someone will let me know, because 15% off is not good. But it is better than giving me 477 if the salifert is correct at 300.

 

[davidwillis]

What does your salt say it mixes to? How do those numbers compare with the results when you use both tests on fresh saltwater?

Why didn't I think of that.... I will give that a try. I use instant ocean which says it should be 400 when mixed at 1.026.

 

[Rusty_L_Shackleford]

But 300 vs 470 does

This to me says either a bad test kit or a testing error. If your lfs does testing (not with api) I would start there. I'm leaning towards the salifert kit being the culprit here because I would be very suspicious of a result that low without it being obvious something is wrong with the tanks inhabitants.

 

[Randy Holmes-Farley]

Be certain you are not reading the Salifert syringe backwards. Many people make that mistake with Salifert kits.

 

[davidwillis]

Fresh mixed instant ocean salt water, should be:
ca: 400
alk: 11
mag: 1350

I think my salifert test is bad. I added the 2ml of water, added the scoop of Ca-1, added .6ml of CA-2 (from 1 to 0.4), mixed for 5 seconds, and it was pink. 0.4 = 300. I also did it again going to 0.5 (adding 0.5 rather than 0.6 initially). It was blue, but turned pink at 0.4 - 300. The kit says it expires 07-2026, but I think it is bad.

Salifert:
Ca: 300
alk: 10.5

The Trident
Ca: 513
Alk: 10.11
mag: 1417

This is not inspiring much confidence in salifert or trident. It seems the Trident is 100 high, and the salifert is 100 low.

 

[sublime275]

It’s supposed to turn pink after you add the 0.6 ml. Keep adding until it turns blue. That is your endpoint.

 

[davidwillis]

It’s supposed to turn pink after you add the 0.6 ml. Keep adding until it turns blue. That is your endpoint.

my gosh... I can't believe I did that. Now I feel stupid.

After running the test correctly, the salifert gave me 420 on the fresh saltwater, and 400 on my tank water. That seems like it may be correct. I think my trident is reading high.