Low magnesium Q?

[Authentic]

Whenever I do a water change my mag falls to 1200 and needs to be supplemented.i have a 65 gal sps dominated tank and am using instant ocean salt.what may be the reason?

[Authentic]

Whenever I do a water change my mag falls to 1200 and needs to be supplemented.i have a 65 gal sps dominated tank and am using instant ocean salt.what may be the reason?I change 8gal at a time.

[bnumair]

have you checked mag in freshly made IO saltwater? if its low in there it will impact ur main tank after water changes.
also roll your bucket around for a little bit before using it. sometime elements settle in un-even proportions.

[downbeach]

What is your salinity? What are you measuring it with? Is it calibrated?
What are your other parameters? i.e. Ca and Alk.
You may want to start using reef crystals instead of IO, since it will have higher levels of Ca, Mg and Alk. Although 1350 would be a better level, 1200 isn't all that bad. Rule of thumb, is Mg should be 3 x your Ca.

[Authentic]

salinity is .24 with refractometer
alk 8.3
calcium was very high after the water change
mag was low

[Mavrk]

I suggest you test the newly mixed saltwater and see what the magnesium is. IO used to have low magnesium, but changed the formula a few years back so that it should be in the low 1300's. Reef Crystals traditionally has magnesium in the 1400's.

[Wet Dreamer]

Just to chime in, I am dealing with a similar issue, but I was using Reef crystals. My magnesium dropped to almost 1000, i have been fighting to bring it back since, makes me wonder if it is an issue with the instant ocean salt, I have never had problems keeping my mag levels up before I switched to reef crystals!

[bertoni]

I agree that the salt product likely is low in magnesium.

[Big E]

Hmm.......not sure about IO being 1300. I've used it for years and always had 1100 of fresh mixed.

I've always bought 20-30 boxes at a time so it's usually quite a few years between when I buy it............but I have recently bought a new box & it tested 1050 with a Salifert kit. So from my perspective, nothing has really changed.

That's interesting about the granuals...........I think I'll mix them around for my next batch to make sure.......although they are bags & not in buckets.

[bertoni]

The old recipe was 1100 ppm. I used that version for years, too. They updated the product fairly recently, and it now should be more like 1300 ppm for magnesium.

[Big E]

How recently? The poster from above said a few years ago.

I bought a box in December & one two weeks ago(1050). The one in December '11 was 1100(LFS).

I'm just trying to nail down the timing, because I'm now questioning if my Mg test kit is accurate. I don't dose Mg, but it would be nice to know what my make up water is. I usually test a new box.

[downbeach]

I would double check the Mg test kit. What do you use to check salinity? Calibrated?

[bertoni]

A few years is about right. I'm not sure why your boxes are so low. Do they have batch dates on them?