You pick the change poll

[sphelps]

Originally Posted by Aquattro

Let's expand on this. What is "very low" and what would the problem be? Mine is about 1150ppm and I don't really see any problems. Looks like a lot of work to chase a number without understanding the problem.

IME low mag = unstable Calcium & Alkalinity. Magnesium helps allow for supersaturation of calcium carbonate so the lower the mag the lower saturation level. My understanding is anything under 1200 ppm is low but then again if you're happy with your current Ca and Alk levels then Mag is likely fine at whatever it is even if lower than 1200ppm. However higher mag levels should result in higher efficiency from a Ca reactor and perhaps better growth as well, whether or not this would be noticeable though....

[Delphinus]

I'd consider 1150 to be in the "good enough" levels. I think basically 1000-1100 or above is sort of my own threshold. I think NSW sits around 1300. I haven't seen any adverse effects having it as high as 1400-1500. I haven't tested any higher because it takes a surprising amount of Mg to raise the levels at all so going any higher than that wasn't economical. I would imagine, however, that there is a point where it's too high and could cause problems .. I just haven't empirically tested for the limits.

When I did notice problems with low Mg, I found that Mg was somewhere around 600-700 and it was due to the salt I was using at the time. Not sure if I had a bad batch or a bad brand but it was one of those little life lessons where the takeaway was that you should test your incoming salt from time to time. (One more reason I choose to stick with IO these days: it's been the most consistent for readings out of any I've tried, and if the levels aren't exactly optimal, they are at least the same amount not exactly optimal from bucket to bucket and I like consistency more than I like paying more for salt that ends up being less consistent.. Oops I just turned your poll into a salt talk.)

In particular, when Mg starts to dip under 1000, I first notice that the anemones expand during the day less than they normally do. This I've noticed enough times (maybe 5 or 6?) that I'm convinced it's not a coincidence. And the lower the Mg drops from 1000, the smaller they get. Also, they start expanding again when I start raising the Mg in the tank (I never adjust more than 100 per day, just for the sake of keeping changes slow).

It is the strangest thing, I don't know why anemones care about Mg, but I'm convinced they do.

Not sure it counts as empirical evidence to back the claim, but there have been a few times people would ask "hey how come my anemones don't expand like they used to" on here, I'd usually chime and say "check your Mg, couldn't hurt" and I seem to recall most, if not all, came back and confirmed that they had low Mg levels. So I'm totally convinced there's a connection, even if intuitively I can't understand why an anemone cares about Mg.

[michika]

Originally Posted by Aquattro

Let's expand on this. What is "very low" and what would the problem be? Mine is about 1150ppm and I don't really see any problems. Looks like a lot of work to chase a number without understanding the problem.

I wouldn't use the word problem as much as I would say it could be holding you back in terms of growth. In my tank Mg is directly tied to the speed at which my clams grow new mantles and how quickly I see growth in most of my SPS.

Magnesium helps in the uptake of Calcium and alkalinity (like vitamin D in bones), or at least that's how I've always understood it.