Tips for performing Red Sea Calcium and Magnesium tests?

[Calm Blue Ocean]

I really have a terrible time figuring out where to stop on these two tests. The end point color between being "purple" and "blue" just both look kind of blue to me just a bit different blue. Anyone have any tips on doing these subtle color things? I'm having some frustrating issues with SPS corals and I know to get some help people are going to want these numbers but I just can't seem to get them to come out consistently enough to report something useful. Appreciate the help.

 

[aggrofish]

IMO when you're that close in color the test results will get you close enough. That far into the test you're talking just a drop or two not a huge difference on the chart. That said theres a noticeable difference between the purple and the blue

 

[LeftyReefer]

I've never had this issue. There seems to be a clear color change for me, from pinkish purple to blue.
Maybe try different lighting? I've always liked this test because the color change is so clear to see.... weird to me that you are having trouble seeing it. That's why I question maybe if your lighting has something to do with it.

 

[Calm Blue Ocean]

I've never had this issue. There seems to be a clear color change for me, from pinkish purple to blue.
Maybe try different lighting? I've always liked this test because the color change is so clear to see.... weird to me that you are having trouble seeing it. That's why I question maybe if your lighting has something to do with it.

I usually do these tests at the kitchen island so good lighting. It's funny, I hate these two tests with a passion.

I always run all my tests before sending an ICP out to help confirm what I'm doing and these two are never right. Just looking at my last one (back in March) my records show Magnesium as 1327 as tested by ATI and 1240 as tested by me. Calcium was 405 from ATI and 380 from me.

Probably time to annoy my other half with more "fish" stuff and get a second opinion on the color.

 

[shakacuz]

these two tests specifically are what made me invest/request(bday and xmas gifts) the hannah checkers for all of the other tests. unfortunately, they do not have a magnesium test kit but i will be purchasing the AF mag kit soon.

i have had to redo the test multiple times and the results are not very consistent. perhaps user error, but i try to be as precise as i can be.

hopefully with the hanna checkers i can have something to fall back to in order to have an average.

 

[PatW]

In my Red Sea Calcium test, I add the titrant pretty quickly until things start to change. The end point is blue changing from purple. You want the blue to be completely blue. Also, if it sits for a very little time, it can edge back to purple. So you have to swirl it for a bit. I don’t know if the test is all that accurate (say closer than 10 ppm). But if used consistently, It is more than good enough.

 

[LeftyReefer]

It sounds like you keep getting results lower than ICP results... which sounds like you aren't putting enough reagent in to get a full color change. You need to add enough of the reagent to where the sample turns a CLEAR BLUE. if its still a little purple, then add more reagent, until it is clearly BLUE. sounds like you are just stopping the test prematurely and calling the color change before its actually changing to blue.

 

[LeftyReefer]

If your ICP test was correct, it should take .81 ML of reagent to get the color change to blue.

Try adding .81 ML and seeing what the color looks like.... is it still purple or blue at that point?

 

[Calm Blue Ocean]

If your ICP test was correct, it should take .81 ML of reagent to get the color change to blue.

Try adding .81 ML and seeing what the color looks like.... is it still purple or blue at that point?

Since it's been a while since I had the ICP maybe I'll try with some fresh mixed saltwater so I have a ballpark number to aim for (hopefully the numbers they claim are somewhat accurate).

Do I keep adding until the blue is completely stable or as long as it shows as blue while being swirled it's good?

 

[LeftyReefer]

If it turns blue, and then stays blue after a few swirls, you should be good to go. If it is turning back purple-ish while you are swirling it, add more titrant until it stays blue while swirling. It may start to turn puple-ish after a minute or so while sitting.

 

[muzikalmatt]

For the calcium test, I tend to add the reagent until I notice the first hint of blue and note the amount used. I'll then continue to add single drops and see if the shade of blue changes/deepens at all. I've found that typically it takes another drop or two for me to get the "full" color change and that's what I consider to be the accurate reading. However, this probably isn't a big deal as it amounts to a difference between a measurement of 400 ppm and maybe 430 ppm, which is within the margin of error for the test anyways.

 

[Calm Blue Ocean]

If it turns blue, and then stays blue after a few swirls, you should be good to go. If it is turning back purple-ish while you are swirling it, add more titrant until it stays blue while swirling. It may start to turn puple-ish after a minute or so while sitting.

Thank you for the tips, hopefully I can get some better accuracy out of these tests.

For the calcium test, I tend to add the reagent until I notice the first hint of blue and note the amount used. I'll then continue to add single drops and see if the shade of blue changes/deepens at all. I've found that typically it takes another drop or two for me to get the "full" color change and that's what I consider to be the accurate reading. However, this probably isn't a big deal as it amounts to a difference between a measurement of 400 ppm and maybe 430 ppm, which is within the margin of error for the test anyways.

Good idea to note the first hint of blue before continuing on. Sounds like I'm being overly conservative with the test and just need to push a little past that first indication.