You pick the change poll

[Aquattro]

Originally Posted by Aquattro

Hmm. Mine is (being generous) ~1170. I'll test alk, pretty sure I have a kit for that

Alk is 8dKh. Sounds good to me?

[kien]

Originally Posted by Aquattro

Alk is 8dKh. Sounds good to me?

If your Alk is fine and you're not finding it difficult then I personally would not worry about mag. I use Alk as my indicator for potential mag issues. My mag as been as low as 1100 and the only thing I noticed when I had it that low as that it was more challenging for me to maintain my Alk higher. It certainly wasn't the end of the world. I have never dosed mag and have only tested for it once in the past 3 years.

[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.

[Delphinus]

As far as the relationship from Mg to Ca and Alk .. yeah, there's a bunch of fancy articles you can read but my main take away from all that is "it takes more Ca and Alk dosing to maintain more gooder levels of Ca and Alk when Mg is low."

So raising your Mg a wee bit (because I don't think I'd worry too much about 1150, although if it were my tank I'd bump up the Mg on the next water change) I'd expect that you might need to bump down your Alk and/or Ca dosing by a wee bit. That said, you might not need to because who knows maybe the uptake will increase thus keeping everything stable, except maybe stuff grows a tiny bit faster. (A bit of a stretch but who knows..)

[Delphinus]

Also from back when I did run a reactor for Ca and Alk, I found that Mg just worked out to where it needed to be.

I've been kind of thinking actually of putting a Ca reactor back online on my tank. When I look back I always had way better SPS growth on tanks with them than without them. I just don't cherish the thought of needing to refill CO2 tanks every few months (which for me was sort of the ultimate push away from a reactor in the first place). I wonder though, if one could just just keep the Ca and Alk dosing and have a small reactor as a kind of supplementary measure and then it's not as big a deal to take the reactor offline for a week to get a tank refilled or whatever.

[Aquattro]

Originally Posted by Delphinus

Also from back when I did run a reactor for Ca and Alk, I found that Mg just worked out to where it needed to be.

I think that this may be the case and I'll just leave well enough alone.

Why were you filling your CO2 so often? I have a 20lb tank and I fill it every 10 months or so. Unless I muck up the gasket, in which case I fill it twice in two days

[sphelps]

Tony if you buy a tank at Oxipro in Calgary they do instant exchange so no waiting. I also have two tanks so ideally always have a back up but I use the CO2 for my keg as well so dual purpose for me.

[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.

[Aquattro]

Originally Posted by michika

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.

That makes sense from what I've seen in other's tanks. But I'm happy holding growth back with SPS. Growing faster isn't always a good thing