Mg test Kits Salifert vs Elos

[morphlingman]

I just finished testing my tanks water parameters. I picked up a new Salifert Mg test kit today, so I wanted to try it out. But first I used my Elos Mg Kit (purchased Feb 12, 2008) to see if they would get a similar reading. To my surprise they showed very different results.
1st test with Elos =1300 ppm
2nd test with Salifert = 1455 ppm
3rd test with Salifert = 1620 ppm
4th test with Elos = 1400 ppm
5th test with Salifert = 1560 ppm
I like the Salifert kit because it has the potential to show greater accuracy, by showing concentrations within 15 ppm. Where as the Elos kit shows only within 100 ppm.
My question is which kit is more reliable (acurate)?
Should I just take the average of all 5 tests to determine an appoximate result? (1467 ppm)

 

[bertoni]

That's a tough set of questions. I'm surprised the numbers for the Salifert vary so much. I've gotten better repeatability. The Elos results are within one drop, which is fine.

I don't know of any data about the accuracy of Mg test kits.

 

[Billybeau1]

There are only a couple of hobby grade kits that provide reasonable results that I've tested.

There is a lot of test noise in hobby grade magnesium test kits and some drifting is not uncommon.

When I tested Elos mag kit against Saliferts, I found close results when doubling the Elos sample.

Sometimes, with the Salifert, it is just a matter of interpretation or the final color end point.

When the color in the vial turns clear, that is the end point IMO.

 

[USC-fan]

So don't add drops until it turns blue? That is what I been doing.

 

[morphlingman]

USC-fan: I don't understand? The test kit says to add drops until it turns blue or gray. If I don;t keep adding drops until the solution changes colour, I won't know what the result will be.

 

[IslandCrow]

I think USC-fan was just asking if he should keep adding drops until it turns blue. From what I've seen (and I believe this is what Billybeau is getting at) is the liquid usually turns a very light grey/clear color before it turns blue. As morphlingman stated, the directions say to add drops until it turns blue or gray, so whichever happens first.

I'm also suprised there was that much variance in the Salifert test results, although I have occasionally gotten results from Salifert (about 5% of the time) that I was pretty sure was wrong and they were significantly different when I retested. I always figured I just made a mistake. . .had an airbubble in the syringe, added too much of one of the chemicals, or something like that.

 

[Billybeau1]

Yes, when the vial turns clear, I call this gray. I believe this is the true end point.

 

[USC-fan]

Okay so I just its time to re-test....

Billybeau1 have you tested this against other test kits and that is why you say that is an end point?

Also what happen to the Salifert section here?

 

[Billybeau1]

Yes, I have tested that to be the accurate end point.

I can't answer as to what happened to the Salifert forum other than the owner got sick and there was so much bashing that RC shut it down.

I still think Salifert makes a fine test kit and stand by them from my testing.

 

[morphlingman]

Thank you for all your opinions, I will try and watch for the solution turning gray before it turns blue. Mine seemed to turn blue straight from purplish pink color, but I will keep a close eye on it. I will test again tomorrow.
Thanks again

 

[Billybeau1]

When you get close, just make sure you swirl the vial after every drop or two. You will actually see the pink disappear.

Mag kits are extremely touchy.

 

[reeferboy83]

I know this thread is old but just stumbled upon it. I have an issue with the salifert Mag test kit, it never turns gray or blue? I have taken my water and had it tested at the lfs and they told me my mag levels were around 1350 but I just bought a new kit so I was trying it out. Any ideas why my water isn't tuning gray or blue when I test it?

 

[bertoni]

You could try using a second syringe to see whether you get a color change. It's possible that the kit has failed, or that the magnesium is over 1500 ppm. Given the problems we see with test kits, it's hard to be sure what's happening.

 

[reefnut81564]

I've been using Salifert kits but have been noticing lately an inaccuracy when drawing the last element (#3) into the test vial. The syringe at times would draw in liquid up to the .80 line and as high as the .85 while the bottom of the black piston is at 1.00. I'm trying to figure out what the right level should be.

 

[shikhyung]

Mag Salifert test kits between mine and my friend (different batch, but both "new" to us), mine is almost 100ppm lower. I tend to trust his because he said he did double check with LFS....

 

[PGUY1]

I've been using Salifert kits but have been noticing lately an inaccuracy when drawing the last element (#3) into the test vial. The syringe at times would draw in liquid up to the .80 line and as high as the .85 while the bottom of the black piston is at 1.00. I'm trying to figure out what the right level should be.

Draw the black stopper up to the 1.00 line, there should be a pocket of air below it. This compensates for the tip that you add to the syringe.

 

[reefnut81564]

I am drawing to the 1.0 line and the gap is inconsistent each time. Some times the solution is at .80 and has been as high as .85. I've been trying to figure out if the gap should be .80 or closer to .85.

 

[PGUY1]

I haven't noticed that. Maybe I need to check mine.

 

[zoolan70]

I've been using Salifert kits but have been noticing lately an inaccuracy when drawing the last element (#3) into the test vial. The syringe at times would draw in liquid up to the .80 line and as high as the .85 while the bottom of the black piston is at 1.00. I'm trying to figure out what the right level should be.

I've noticed that too. I just operate under the assumption that it will all average out over time.

 

[bertoni]

The amount of air doesn't matter, as long as the syringe is dispensing liquid when the plunger is moved. I never paid any attention to the volume of air. There are a few factors that might influence it, including how tightly the plastic tip was fixed on the main body of the syringe.