I'm liking the Seachem Reefstatus Calcium and Magnesium kits. Accurate and precise, but maybe a bit more demanding on your lab technique. The Seachem kit is nice in that it's picky enough to precipate Ca before titrating the Mg, so that Ca doesn't throw off the Mg reading. I used the Seachem Mg for the first time last week.
I like the Salifert Magnesium kit, but the type I've been using doesn't resolve Ca from Mg, and the accuracy depends on your Ca being in some particular "normal" range. I saw some info that implied the newer Salifert kits actually measure Mg separately from Ca now.
I've been using Salifert Alk test. Fast and easy, accurate and precise as long as you didn't get one of the bad batches a while back.
I think Salifert has been reworking its line of kits. A lot have been unavailable, and I see that DF&S will be selling them starting Jan. 15. The DF&S info is different compared to the old kits.
Haven't used Elos, but lots of people like them because they are easy to use and have sharp transitions on the color change. If you look at the specs, one of the things that contribute to this is that the resolution on their test is low compared to Seachem or Salifert.
Their Mg kit is precise only to 100ppm compared to 12.5ppm for Seachem and 15ppm for Salifert. I take it that the kits are accurate though.
The Elos alk kits can do 30 tests that resolve to 1 dKH, or 60 tests that resolve to .5 dKH. Salifert can do 100 tests that resolve to .15 dKH, or 200 tests resolving to .3 dKH.
If you take the precision tip off your Salifert alk test, you can still test within .6-.7 dKH even if you only want to do full drops, and you'll get a sharp color transition like on an Elos.
Guess I sound pretty underwhelmed by Elos. But to me, it's like trying to bake a cake, and your smallest measuring cup is 8oz.
Here's a cool trick. Take a precision tip from a Salifert kit and stick it on your Seachem syringe for tighter readings
