And I quote a site on the web....namely:
http://www.aquarium.net/0497/0497_3.shtml
Magnesium is roughly three times more abundant than calcium in natural sea water (1.295g/kg versus 0.412g/kg). Yet it plays a vital part in the whole carbonate scheme of things. This is what keeps the oceans supersaturated in respect to calcite.
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So your magnesium is a bit high (about 2x what it should be), but from what I was reading, it won't make much difference to living things (at least, not in a detrimental way).
Here's something else I found...
http://www.animalnetwork.com/fish/library/articleview2.asp?Section=&RecordNo=2856
Magnesium: Calcium's little sister
by Randy Holmes-Farley
Magnesium is an interesting atom that has tremendous biological and chemical relevance to reef tanks. Fortunately for reefkeepers, it is present in abundance in seawater and is depleted only slowly. Consequently, maintenance of magnesium levels is not typically a big issue if using an appropriate salt mix. Nevertheless, magnesium is a very important ion and engenders much discussion among hobbyists. In this article I'll try to add to the extensive writings that Craig Bingman has published in the past.
First, a little background on magnesium. In seawater, magnesium is invariably present in the form of a divalent cation,
Mg++. It is present in seawater at a concentration of about 1300
ppm, and that concentration does not vary appreciably with depth or location in the world (besides estuaries and other places where all ions are distorted). In seawater,
Mg ions outnumber
Ca ions by a factor of 5. Most magnesium in seawater is present as the free ion hydrated with tightly bound water molecules. Some of it, however, forms tight ion pairs (i.e., soluble complexes) with negatively charged ions, such as sulfate, bicarbonate, carbonate, borate, fluoride and hydroxide.
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Personally, I'd just do a few water changes and then recheck it. Also, recheck your test kit against the baseline they give.
Kevin Colagio
Reef Geek.
http://www.PersonalReefs.com