View Full Version : Mg Test Discrepancy - Salifert vs Elos
yeldarbj
04/25/2010, 01:37 PM
I recently bought an Elos Mg test kit, having always used Salifert in the past. I decided to test using both kits, while I have a few more Salifert tests before it runs out, just to make sure they test fairly close to each other. I've test 3 times over the last 2 weeks, and I'm getting some huge discrepancies. The Elos results are much higher in each test.
1410 (Salifert) vs 1600 (Elos)
1410 (Salifert) vs 1700 (Elos)
1470 (Salifert) vs 1850 (Elos)
Anyone else with similar experience? BTW, my mag levels are intentionally high to treat a bryopsis outbreak.
HighlandReefer
04/25/2010, 02:31 PM
You could mix up a batch of your salt water to a salinity of 1.0264 using a properly calibrated refractometer and compare your results to those that Billy gets in this link. It would give you some idea of how the kits compare.
A General Guide to Salt Mixes
http://www.reefcentral.com/forums/showthread.php?t=1714505
Kshack
04/26/2010, 08:07 AM
YES! I got the exact same results and called Elos. He said there were no reports of bad test kits and that high mag would not be a problem. I have not added mag for 3 months and the test (Elos) shows 1700. My mag was always around 1200-1300 with Salifert.
yeldarbj
04/26/2010, 11:27 AM
So I mixed up a batch up water with Seachem Reef Salt to sg of 1.026.
Bertoni's Results vs As Tested
Alk 10 vs 9.1 (Salifert)
Cal 540 vs 440 (Salifert)
Mag 1450 vs 1080 (Salifert) vs 1300 (Elos)
The results make me want to assume that the Elos test kit is closer to correct. I wish I had Elos Alk & Cal kits to compare as well.
stanlalee
04/26/2010, 12:02 PM
So I mixed up a batch up water with Seachem Reef Salt to sg of 1.026.
Bertoni's Results vs As Tested
Alk 10 vs 9.1 (Salifert)
Cal 540 vs 440 (Salifert)
Mag 1450 vs 1080 (Salifert) vs 1300 (Elos)
The results make me want to assume that the Elos test kit is closer to correct. I wish I had Elos Alk & Cal kits to compare as well.
I wouldn't neccessarily assume that. I and many people have had batches of seachem reef salt with low mg (some reported as low as the 500's in fact. I got 1050 using elos).
HighlandReefer
04/26/2010, 02:37 PM
The only real way to properly compare the test kits is to use a known standard that is in the range we operate at. ;)
Did you use a properly calibrated refractometer (using a salt standard) to measure your salinity? Hydrometers can be off significantly in some cases.
yeldarbj
04/26/2010, 03:22 PM
Yes, I used a freshly calibrated refractometer. I was really just wondering if anyone else has used both kits at the same time, with the Elos results being 10-25% higher each time.
With the salt mix test, I understand that there will be difference between batches and even bucket to bucket. Given my tests were ~10% off for Alk, ~20% off for Cal., the Elos Mg test falls within that same error range whereas the Salifert test exceeds it. It easily could be the case that the Alk & Cal tests are out of whack too.
HighlandReefer
04/26/2010, 03:29 PM
One reason why it is suggested to shoot for the middle of the recommended ranges for our parameters, is due to problems with hobby grade test kits. This is a common problem amoung hobbyists.
I would use the middle ground between the two test kits as your reading. ;)
bertoni
04/26/2010, 07:31 PM
The rate of problems with test kits is very high. I'm not sure what I'd do here, but I'd be tempted to get opinions with other test kits, if that's not too difficult.
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