Most accurate magnesium test kit?
- Thread starter kashman100
- Start date
- Tagged users None
Labridaedicted
Wrassetastic
I've found the red Sea pro titrations to be fairly accurate.
20ppm isn't a huge deal on mg, though.
20ppm isn't a huge deal on mg, though.
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
I agree that 20 ppm is within both the likely error of the kits, and the precision we actually care about anyway. 
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
If the values are between 1250 and 1500, it is fine and the exact value does not matter.
I did a cost/accuracy comparison between the new(at the time)Red Sea Pro Kit containing all three: Ca, Mg and Alk, and Salifert kits bought individually, 5 years ago. The accuracy results were negligible, but the cost of the Red Sea was significant, considering you could buy refills for the kit. The one exception was the Alk test that came in a little less expensive for Salifert($.14 per test for Salifert vs $.16 for Red Sea Pro kit). The Red Sea Mg kit was consistently 10ppm higher than the Salifert, again, a negligible difference. I retested six month's later with similar results.
Yes, here is the last paragraph from that post where I did a comparison:
"The one caveat here is that the Red Sea kit calculation is determined by taking your end point reading from the plunger in the syringe and deducting it from the 1mL you started with to determine how much of the titrant was used, i.e. if the reading on the syringe is .37 you used .63, which is the number you need to determine your reading. It isn't hard, but you have to do the math, and I see it as an area for potential human error. The Salifert kit just gives you the reading without the user having to do any additional calculations."
Randy Holmes-Farley
Reef Chemist
Staff member
Super Moderator
Excellence Award
Expert Contributor
Article Contributor
R2R Research
My Tank Thread
With any hobby titration kit where you add liquid until you get to a color change, more liquid dosed should give a higher value for the final result.
If that is not the case, you are reading it backwards.
If that is not the case, you are reading it backwards.
William Robinson
Active Member
This is a fairly old thread. However I think it should be revived. Ive read through the response and agree with the statements of values between xxxx and xxxx are perfectly acceptable. Again however, due to BRS having Magnesium additive now and the use of their calculator to determine weekly usage for us that use automated dosing equipment it is important to accurately be able to determine our level of decrease in a 5 day period which I have not found a reliable method of do so thus hesitant about dosing my magnesium. I have tried 3 different kits since January 26th from the Red Sea, Salifert and yes... API. Each of these were fairly close but none have indicated a usage rate. Below are in sequential order the test results.
1/26 1120 API (Expired)
1/28 1320 (RS)
1/29 1350 (RS)
2/3 1300 (RS) - Too big of drop so I was suspicious
2/5 1350 (Salifert)
2/6 1300 (Salifert)
2/11 1365 (Salifert)
As you can see its all over the place and even the Salifert for the 5 day period needed by BRS Calculators are erratic. Has anyone found a more reliable method since this was last updated?
1/26 1120 API (Expired)
1/28 1320 (RS)
1/29 1350 (RS)
2/3 1300 (RS) - Too big of drop so I was suspicious
2/5 1350 (Salifert)
2/6 1300 (Salifert)
2/11 1365 (Salifert)
As you can see its all over the place and even the Salifert for the 5 day period needed by BRS Calculators are erratic. Has anyone found a more reliable method since this was last updated?
Larry L
Valuable Member
Assuming your actual value is somewhere in the middle, these numbers are all within 1132 +/- 2.5% which is probably well within the margin of error for any hobbyist test kit.
William Robinson
Active Member
Oh I realize that and I realize the numbers are good as well. My irritation I guess is with the BRS dosing calculators that use a 5 day testing period. I guess I'll just have to average my results and then do a 10 day test and maybe a 15 day test to get a better usage number.
