What can influence a tank's Mg reading

[Delphinus]

Ok sorry, I meant mix the salt itself, not the water with salt in it. I once complained about another premium salt brand that was reputed to have Mg at 1400, but when I tested Mg, it was 900. (I'm actually really starting to wonder if the problem is Elos can't tell me if Mg is <900 - it clamps at 900 - just on account I've never had a reading less than 900). Anyhow, I ranted about it, and one thing that came out of those conversations was that you're supposed to mix salt before you use it. For real. Isn't that the lamest thing? But I guess if they're adding this and that when they're making the salt up, the proportions may be all correct as far as the total batch is concerned but the dispersal may not be as homogenous as one would like.

Tank with the flatlined Mg is not new and has no sand. It has maybe a half dozen 1" SPS frags, two smaller colonies, a bubble coral, a gigantea carpet and two ocellaris. Maybe about 3 billion aiptasia though. It's a 24x24x12 shallow lagoonal thing.

Ca is 360, Alk is 7 and Mg is 900.

The other tanks have similar but different readings. One has Ca 420, Alk 7 and Mg 1100 (as of last night anyhow, I am still raising it though), the other has Ca 370, Alk 7, and Mg 1050 (also still being raised). One other is a BB tank, and the last one has a 1" skiff of sand.

I am betting dollars to donuts now that the issue is in fact the test kit can't tell me a number less than 900. I will test tonight with Salifert and see what shakes out.

[StirCrazy]

Originally Posted by Delphinus

I am betting dollars to donuts now that the issue is in fact the test kit can't tell me a number less than 900. I will test tonight with Salifert and see what shakes out.

If the salinity levels are the same I am with you on the test kit.

no reason for excessive Mg consumption in your tanks.

Steve

[Delphinus]

Salifert says 1005, Elos still says 900 tonight.

I was wrong about Salifert resolution at 30, it's 30 units apart on the lookup sheet but going up in 0.02ml increments. So it's really 15.

I also dropped the vial for the Elos test kit and shattered it into about a billion little shards. Yay me. Man those things break super easy.

[Myka]

Hmmm...that's interesting that the two kits are so far off from eachother. I "hate" it when that happens. Could it be that the kits are only off by like 30 or 40 from eachother, but because the Elos jumps by 75 per drop it's showing 105 off?

[Delphinus]

Yeah, I'm not too pleased with the disparate readings. I don't think I've ever had the two read exactly the same but it's never been this far apart. I wonder which one is slipping. Ugh, I hate test kits. Although at least they give me a rough ballpark if nothing else.

[Delphinus]

So I've confirmed now that Elos simply can't tell you anything less than 900.

And I've confirmed that my RBS salt has very low Mg at 825.

Ugh, well, at least that mystery is solved.

[RuGlu6]

So i guess we are now back to a question:
What is the best reef salt out there