Alk Test Kits

[bdare]

Got my LaMotte last night...

I'm really not that impressed. The color change is very difficult to decipher.

 

[Canarygirl]

Just use it a few more times and you'll get the hang of it. Using the card for color matching is very helpful at the beginning.

 

[bdare]

Yeah... I think it's the inbetween color that throws me off. It's tuff to tell when it goes from the inbetween to the "I'm done" color.

 

[Nanz]

<a href=showthread.php?s=&postid=11630127#post11630127 target=_blank>Originally posted</a> by bdare
Yeah... I think it's the inbetween color that throws me off. It's tuff to tell when it goes from the inbetween to the "I'm done" color.

As long as you see that wine color and its not orange then thats the endpoint. This kit is extremely accurate and even if you make a mistake your still going to have a better result than a test kit that reads drops in dKH.

I compared my results today with my lab and my Alk was dead on in ppm. But then I got alot of practice. Im going to start a study with our lab to compare tests against my kits ove the next 10 weeks. Once I have collected 5 or so sets I will display my results so you can see the trend of hobby test kits vs lab grade instruments. So far the Alk on Lamotte was exactly the same as my lab results except I only report Lamotte in ppm and the lab reports in ppb, hehe.

I will share the data when its complete.

 

[bdare]

NIIICE!!!

I look foward to your results.

 

[pdkinsel]

<a href=showthread.php?s=&postid=11631013#post11631013 target=_blank>Originally posted</a> by bdare
NIIICE!!!

I look foward to your results.

Same here, looking forward to the results.


Had old salifert alk kit that read 9.9, new salifert kit (purchased from MD a month ago or so) read 8.0, used seachem total alk and read about 8.3 or so. How does one tell if they have a bad salifert test kit?

 

[Billybeau1]

Hobby grade test kits have some test noise anyway. Anyone who thinks they are going to get accurate results every time from a hobby grade kit is sadly mistaken.

Most of these kits are within 2 dkh or so from each other and I believe consistency is the key here.

As long as you test with the same kit, and your tank looks good, I would not get hung up on the numbers.

Some reefers tanks look good at 7 dkh and some look good at 12 dkh.

Your eyes are the key. Test kits just tell us when things are different from what we are used to.

No wonder Randy hates testing. I'm beginning to see what he means.

His tank looks good to him so why worry about water parameters.

 

[Obi-dad]

The point (for me) is not that I get absolute accuracy of a measurement, but that I get repeatability and more precision than 1 dkh. So when I get 8.4 on the old Salifert kit, it may really be 8.8, but I get the same result every time on my old kit, so the difference is not important - but I get better precision from the old salifert kit than the 1 drop = 1kh from these other kits. There is a difference between accuracy and precision (which I probably haven't explained very well).

I don't mind using the 1 drop per dkh for routine measuring, but I would much prefer the higher precision of the old salifert kit for tuning dosing or calcium reactor setup (even if the absolute value of the measurement is not exact). Hopefully Salifert will come back at some point.

 

[Nanz]

<a href=showthread.php?s=&postid=11639649#post11639649 target=_blank>Originally posted</a> by Obi-dad
The point (for me) is not that I get absolute accuracy of a measurement, but that I get repeatability and more precision than 1 dkh. So when I get 8.4 on the old Salifert kit, it may really be 8.8, but I get the same result every time on my old kit, so the difference is not important - but I get better precision from the old salifert kit than the 1 drop = 1kh from these other kits. There is a difference between accuracy and precision (which I probably haven't explained very well).

I don't mind using the 1 drop per dkh for routine measuring, but I would much prefer the higher precision of the old salifert kit for tuning dosing or calcium reactor setup (even if the absolute value of the measurement is not exact). Hopefully Salifert will come back at some point.

Its best explained by thinking of a dart board. Three darts grouped together is precision even if the are no where near the bullseye which is accuracy. If you can perform 3 tests with the same result then you have high precision. But if your test kit reports in 20ppm units then you really are not being that precise because you have no idea where you are in the 20ppm range and its not that difficult to replicate the result. However with a testkit that reports in 5 ppm its going to be more difficult getting the exact same result yet all the results may be in the 20 ppm range.

 

[bertoni]

Technically, I think the three darts clustered together is repeatability. The precision is the distance between the lines on the board. Isn't that the standard terminology?

 

[Obi-dad]

I should have used the word 'resolution' in addition to 'repeatability'. The old Salifert kit has higher resolution than the 1 drop per dkh kits, which is more useful for fine tuning calcium reactor and dosing systems. By repeatability I was just saying that when I take 3 test using the old salifert kit from the same water I was getting the same reading - even if it is off from a more accurate test, I don't care because I am getting repeatability with more resolution than using the 1 drop per dkh kits.

For routine measuring, the 1drop per dkh is fine.

 

[Nanz]

<a href=showthread.php?s=&postid=11654954#post11654954 target=_blank>Originally posted</a> by bertoni
Technically, I think the three darts clustered together is repeatability. The precision is the distance between the lines on the board. Isn't that the standard terminology?

Yep, you are correct.. I was trying to explain that without using the word standard deviation and all I could think of was a dart board.

 

[bdare]

Well...

I picked up an API KH test kit yesterday. I have to say I think it works very well. My plan will be to use the API kit for spot checking and use the LaMotte for updating my dosing schedule.

Ben

 

[Billybeau1]

Inexpensive, easy to use and good end point. Thats why I like them.