Salifert v. Seachem Ca Test Results

[steve the plumb]

I guess I will test with both kits and settle for a 50 ppm inbetween.If I stay above the 400 ppm mark I am fine.My friend has the american pharm test kit and he says its supposed to be a good test kit for $11.99.I will ask him to bring it over just to see what that tests at.

[poormanisme]

i have had similiar results with the last 2 salifert CA kits when compared to Seachem's CA kit. My water tested ~400 with the Seachem kit and ~500 with the salifert. At first i thought i just got a bad salifert kit so i bought another and had similiar readings. To be honest im not too concerned as all my SPS are doing great but it sure would be nice to know what is going on with the CA kits these days.

Scott

[leebca]

Steve/Plumb,

I can get the Seachem Ca test kit in the US for $25 or less. I think the $45 CDN then would be about right? Maybe not.

Please let us know the results from American Pharmacy kit.

I think you're right, like Randy wrote. If you're over the target value, you're okay.

[steve the plumb]

I usualy buy stuff from the U.S. its half the price.I found the Seachem for as low as $20 us.The US dollar is low about 25 to 30 cents so it would cost me about $26 cdn plus shipping.I send the stuff to my cousin and pick it up.His wife just came here I should have ordered it but I wanted to know.My friend came by I didn't have a chance to ask for his test kit but I will try and pick it up.I will retest with all 3 when I get it.

[steve the plumb]

My friend works at hagen I can ask him to get me a test kit aswell

[RustySnail]

Randy/Chemists-

Is it possible that one of these kits actually reports mg/l instead of ppm? Would the difference between mass/volume measurement to the ratio of ions be enough to account for the discrepancy?

[Randy Holmes-Farley]

No, the difference between ppm and mg/L is only about 1.023, or about 9 ppm. I explain that difference in my latest article:

The Units of Measure of Reefkeeping
http://reefkeeping.com/issues/2005-08/rhf/index.php

[MoonDark]

I kinda have a theory about this... Its about the air present in the sringe...

You see ( I am at the university at this moment so I dont have the salifert test instructions )...

When I fill the sringe the air present in it its about 0.2 ml ... If I dont drop anything in my test sample ... and I go to the test comparison table, it says that 0.8 ml = like 100 ppm Ca ( or something like that , right??? ) that has always bugged me a lot , and I dont know whats it about... I will try to see the instructions at night and then ill report to you .

[Randy Holmes-Farley]

Salifert kits are supposed to have air inside the syringes, and that is exactly taken into account.

[wrassie86]

Ive always liked the american pharm test kits and found them to read the same as salifert for alot less money.Last time i tested the calcium kits back to back they were real close.Also i tested a seatest kit at the same time and it was way off.When salifert and american pharm read 440-460 the seatest read 370.

Also as far as nitrate kits, i think the american pharm blows the salifert away.

[MoonDark]

But it doesn't say, how much air is counted to be present , if I fill the sringe fast , I can get less air into it ... so that is not clear I think...

[MCary]

I compared my Seachem Kit with a Dade Expand Chemistry Analyzer. They correlated very well. FYI.

[Hobster]

Originally posted by MoonDark
But it doesn't say, how much air is counted to be present , if I fill the sringe fast , I can get less air into it ... so that is not clear I think...

You can always take the fine tip off the syringe and just fill it to exactly 1ml. When you test, it will be larger drops so each drop will be a factor of about 25 (IIRC) It seems (from this thread) that any of the kits are not that precise anyway.

[wrassie86]

Originally posted by Hobster
You can always take the fine tip off the syringe and just fill it to exactly 1ml. When you test, it will be larger drops so each drop will be a factor of about 25 (IIRC) It seems (from this thread) that any of the kits are not that precise anyway.

Yup take it off,fill up,put the tip back on and force the air out and pull more soulition in.If that makes any sense

[Hobster]

Just don't use the tip at all. Plus it's faster than all those tiny drops. +/- 25 ppm. I don't think we are going to be accurate to 5 ppm.

[Habib]

Originally posted by MiddletonMark
I believe Habib is on vacation, otherwise he'd be here probably giving a detailed explanation.

What you want to believe, that's each of our own choice.

But with him on vacation, we're just going to have to wait for him to chime in.

Yes, I was on vacation and came back today.

Interesting thread and I will certainly add a few things here the coming days.

FWIW, if the Salifert is performed correctly then it should give results, using seawater or something similar, within approx 8 mg/L of the actual value.

[BeanAnimal]

type fast habib.... It's been a long wait!

[Tom_Nev]

I have an Aquarium Pharm and a Seachem for the basic tests (Am, NO2, NO3, PH). For the price, I think the SeaChem wins hands down. I also have the SeaTest kit for Ca, Phosphate and low range NO3.

I actually use the Aq. Pharm most, but only to determine if there is any significant change in water chem. With Aq. Pharm. kit I've just benchmarked the results (because the actual test results are flawed and have too large a deviation; see below) and when I test I look for changes intead of numbers.

There is an inherent problem with color matching cards which are digital (i.e., 6 or 7 unique color blocks associated with a reading like 10 ppm NO3 with a shade of yellow, 40 ppm with a shade of orange). Depending on the light spectra the card is viewed under, in my experience, the result may be perceived differently (in the Aq. Pharm kit, PH, depending on where I view it, sun, fluor or "full spectra" the same result looks like 8.0 or 8.4). Additionally, there are times when the test result color does not match the color block exactly, introducing large amounts of error (i.e., result color between 20 ppm orange and 40 ppm orange could mean 21 ppm or 39 ppm {extreme example} which is significant error, not good).

The Seachem tests that use color matching cards are analog (or a gradient) a continuous incremental color shift along the length of the card, which means you can always match the test result color to SOMEwhere on the card.

The best hobby tests IMO are the ones that titrate, with a resultant shift from blue to yellow, counting drops. No mistaking a blue to yellow shift (even if you're color blind). Even better would be blue to red (if possible) a larger bandwidth jump. Most of the cards (digital) do not have enough bandwidth between color blocks to afford a reasonable (indeed necessary) margin for error to make them worthwile if you're trying to read an actual number.

[Habib]

Originally posted by BeanAnimal
type fast habib.... It's been a long wait!

Sorry about that but I was, as mentioned earlier, on vacation and wanted to read most of this thread first.

I did not read all the posts but the impression I'm getting is that there is very likely a systematic difference between the Seachem and the Salifert calcium kits. The Salifert giving a 25-40% higher value than the Seachem.

The colorchange with the Salifert is quite sharp and the end point is approx 25 mg/L after seeing the first purple. If that is not problematic, that is people did stop close to the end-point, then I'm inclined to believe that it is not the Salifert but the Seachem which is giving a deviating value.

We use various standards and include also a few natural seawater samples. We spend 1 -2 days adjusting the reagent to give the desired value and consist of many measurements.

I know some people have used the Salifert for measuring calcium in natural seawater and I can't recall seeing a major deviation (25% or more is a HUGE deviation).

Many people have also reported the values they get for IO through the years and again they seem to be OK.

There was a period in which suddenly people started to report very high calcium values such as 650 mg/L and we rechecked many batches and all were OK. It turned out that they were using Oceanic salt and I contacted Oceanic (several other people too) and the measured values were confirmed by Oceanic.

These Oceanic salt values again reconfirm that the Salifert does not measure with a systematically deviation of say 25% from the true value.

The above statements can be found easily here on RC.

During the years we did recheck many batches for people having questions and in only a few cases the deviation was a mystery (perhaps accidental contamination of the reagent by the hobbyist?) and never batch related.


If there are specific questions about a certain batch someone has then I will be happy to communicate about it in the Salifert forum.

I have no problem with answering general questions about the correctness in general over here.



One comment about the Lamotte calcium measurement. They probably make several very good kits, however, their calcium requires a dilution factor of almost 13 so every error or uncertainity in calcium reading has to be multiplied by 13 as well. So the calcium value obtained with the Lamotte might have a very high uncertainity range.

[BeanAnimal]

Habib,

Thank you for taking the time to try and explain the deviation. As I have not used your kit, I can not comment on the results as compared to the kits I have. I will give your calcium kit a try.

My concern stems from the fact that many companies produce products for profit without regard to their quality. As long as the product sells, then it is regarded as "good" or "acceptable". I see this in our hobby, software, electronics...everything.

At least you have shown that you will take the time to explain and promote one of your products. Many manufacturers don't make what they sell anymore, instead they farm out or rebrand. It is very frustrating to deal with a "sales" person when you have a technical problem or question. Anybody can read from a spec sheet.

[leebca]

Habib,

What would explain the Seachem standard giving their test kit the same results; the LaMotte Test kit the same results; but the Salifert kit 25% higher results?

Should not a standard, regardless of 'systemic' issues give the expected results? Many of the examples you give is measuring the unknowns and measuring against Salifer internal standards. What do the Salifer internal standards read on the LaMotte and Seachem test kits?

I still have a concern when my LaMotte Test Kit reports X Ca; my Seachem TK reports X Ca; and the Salifert TK reports X + .25X Ca. The color change with the Seachem TK is very clear. Enough so that I can tip-off partial drops and see a change.

Thank you. Hope you had a good vacation!

[Hobster]

Habib,
I think part of the confusion stems from the fact that the SeaChem test kit has a "reference" sample. If the actual test matches the reference (as mine did) then it would lead one(me) to believe it is correct.If this is true, I do not know for sure.

Can the reference be such that it only works or matches a specific brand of test kit.? Somewhere in this thread I posted where I tested the SeaChem reference with the Salifert and it was around 500??

I have several Salifert kits and not trying to prove one brand is better or worse, only to find what me actual Ca level is.

Thank you. If Randy wants this moved to your forum, please wave the magic wand.

[trmiv]

My question is, where should you actually stop dropping drops when using the salifert kit? It says when it's "clear blue" what is that? I usually get it to that purple color, and then about 2-4 more drops turns it blue. Is that right, or should I be stopping sooner or later?

[leebca]

Hobster,

It doesn't make sense that a 'reference' only gives a specific number with a specific test. Either the reference is a reference of known Calcium concentration, or it isn't.

So let's think this through. The 'reference' when tested with the Seachem TK confirms the reference concentration. The 'reference' when tested with the LaMotte TK confirms that number. The Salifert test kit says it is about 25% higher in concentration.

Then why, when testing a sample of aquarium water, does the LaMotte and Seachem test both have the same number within their margin of error, but the Salifert TK is still running 25% higher? Shouldn't all test kits work with the seawater they are supposed to test? The seawater results match the reference results.

I'm hoping for a technical/chemical explanation for the above results, because the reference AND water samples run the similar difference doesn't imply the Seachem test is only accurate with the Seachem reference.

[Hobster]

I think I agree with what you just wrote
I am completely confused. I would think that the SeaChem reference of 400 would in fact be 400 no matter what test kit was used. I would like to see what Habib says as I posted my batch numbers in the beginning of this post. Maybe he can check/compare those?

What I would like to know is if there is a homemade reference we can make? Perhaps x amount of Dowflake in a gal of water or something like that.............