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?

[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

[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.

[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 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.

OxyPro for the win. I also do this, but not for kegs.

[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

[Delphinus]

Originally Posted by Aquattro

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

Actually that's about par, it was just an inconvenience to take time off work to go to a place that could refill it (because any such place will only be open when I'm supposed to be at work myself, with the only exception that they open later than when I start, and close earlier than when I finish .... what is UP with that anyhow!!!) and then to have to do it twice (once to drop off, once to pickup).

A tank exchange program would be better.

Ok in the end it wasn't the only reason, I always had issues with the designs of the ones I was using, I also had issues maintaining steady slow flow through those things (would be easier nowadays with peristaltic pumps and controllers so a bit of a moot point perhaps) and plus there was the whole "I want to reduce my CO2 footprint because I *care* blah blah blah".

Like I said I am sort of considering going to back to a reactor. As soon as a few other projects are off the to-do list I was thinking of building myself a new one. Been far too long since I did any acrylic fabrication for this hobby. Might be time to revisit that.