API vs Salifert Calcium test

[LgTas]

I've been using the API calcium test for 8 months on my nano which was reading on average 400 ppm.

I've since setup my 90 gal with predominantly live rock, coral skeleton, and aragonite sand. My API test kit reads 420 ppm. I recently purchased a salifert bundle and tried the calcium test to compare. For some reason it's coming back with 490 - 500 ppm? I've done the test 4 times and get the same result. Got my chemist wife to do it and she got the same. We left the air gap as instructed to etc.

I can only assume that the API is correct and Salifert way off. My seawater I use is aprox 420 ppm naturally.

Any ideas what I'm doing wrong?

 

[reefviper101]

I've been using the API calcium test for 8 months on my nano which was reading on average 400 ppm.

I've since setup my 90 gal with predominantly live rock, coral skeleton, and aragonite sand. My API test kit reads 420 ppm. I recently purchased a salifert bundle and tried the calcium test to compare. For some reason it's coming back with 490 - 500 ppm? I've done the test 4 times and get the same result. Got my chemist wife to do it and she got the same. We left the air gap as instructed to etc.

I can only assume that the API is correct and Salifert way off. My seawater I use is aprox 420 ppm naturally.

Any ideas what I'm doing wrong?

Can not explain the

I've been using the API calcium test for 8 months on my nano which was reading on average 400 ppm.

I've since setup my 90 gal with predominantly live rock, coral skeleton, and aragonite sand. My API test kit reads 420 ppm. I recently purchased a salifert bundle and tried the calcium test to compare. For some reason it's coming back with 490 - 500 ppm? I've done the test 4 times and get the same result. Got my chemist wife to do it and she got the same. We left the air gap as instructed to etc.

I can only assume that the API is correct and Salifert way off. My seawater I use is aprox 420 ppm naturally.

Any ideas what I'm doing wrong?

Can't explain the huge difference between the two but i use api and have for 10 yrs i find them to be reliable but if unsure take sample to lfs and have them test that's what i do just for the piece of mind

 

[Sarcazian]

Take this for what it's worth, but BRS has mentioned on a couple of videos that a test kit is more a matter of knowing change. So, if your avg reading is 400 then you know your levels are level across the test period. So, you know your dosing or good or that you do not have to dose. If you check again and the level is 380 then you know something is using calcium/etc.


I picked up an API based calcium test kit last night from the local Petco. My first test was a major failure since I gave up trying to change the water blue after 35 drops (like 530 or so I think).

 

[Randy Holmes-Farley Verified Community Expert]

I cannot know which, if either, is correct, but in a head to head comparison, I'd believe the Salifert before the API, but be sure you are not reading the Salifert syringe backwards. If you just finish a syringe to get to the endpoint, it is a lot of calcium, not none.

If the salinity is high, the calcium in natural seawater will be high.

 

[LgTas]

Take this for what it's worth, but BRS has mentioned on a couple of videos that a test kit is more a matter of knowing change. So, if your avg reading is 400 then you know your levels are level across the test period. So, you know your dosing or good or that you do not have to dose. If you check again and the level is 380 then you know something is using calcium/etc.


I picked up an API based calcium test kit last night from the local Petco. My first test was a major failure since I gave up trying to change the water blue after 35 drops (like 530 or so I think).

That's a good way of looking at it. I was just concerned about having too much Calcium but I'm yet to read up on what 'too much' is.

I cannot know which, if either, is correct, but in a head to head comparison, I'd believe the Salifert before the API, but be sure you are not reading the Salifert syringe backwards. If you just finish a syringe to get to the endpoint, it is a lot of calcium, not none.

If the salinity is high, the calcium in natural seawater will be high.

Thanks Randy. Yes reading the titration correctly.

Here are the rest of my parameters. It's a new setup so my fuge is still settling but my nitrates and phosphates are on a downward trend

P - 0.25
N - 25
Kh - 8
Mag - 1200
Cal - 420 (API)/500 (Salifert)
Salinity - 1.025

I might try test some local sea water to compare.

 

[LgTas]

Just to close this thread off incase anyone stumbles upon it in the future.

I tested both tests against a control of 415 ppm calcium solution at 1.025 salinity. Results:
Salifert - 420
API - 360

Results speak for themselves.

 

[BigD9.5]

I have both,sailfert all day!

 

[blasterman]

Most of the complaints against the salifert is the titration color change is too gradual and people have a habit of reading it too early. Hence low calcium readings.

If you understand this quirk with the salifert and let the color fully change its a decent kit. However, the half resolution mode is worthless..

The red sea kit is much better for beginners.

 

[William Morris]

Just to close this thread off incase anyone stumbles upon it in the future.

I tested both tests against a control of 415 ppm calcium solution at 1.025 salinity. Results:
Salifert - 420
API - 360

Results speak for themselves.

Where did you get the control solution? Did you make it yourself?

 

[LgTas]

Where did you get the control solution? Did you make it yourself?

Wife is a chemist for the state water authority. She made it up for me at their lab.

 

[Randy Holmes-Farley Verified Community Expert]

Wife is a chemist for the state water authority. She made it up for me at their lab.

Just be careful how you interpret such results.

I assume the standard is not in a seawater matrix, so it tests the titration accuracy, but not the ability of the kit to properly distinguish calcium from similar ions such as magnesium.

Thus, a kit should give the correct result, but that correct result does not ensure it is working correctly in seawater.

 

[Marc2952]

I think the salifert may be the one off, i just tested my new salifert against a new one i jist got today and both where off by 65 ppm which is ALOT. The old one tested at 425 while the new one tested at 490.

 

[dadyoj21]

I also have received the new version of the salifert kit and sampled both my systems (300gal and 400gal systems) with the new and old salifert kits. system 1 new kit 540 old kit 480. system 2 new kit 490 old kit 420.

The new kit is reading 60-70 ppm higher than the old. Since I have been using the old version for 10 plus years with no system problems I am assuming the new kit is not accurate and reads way high.