What can influence a tank's Mg reading
 

I fell off the wagon for Mg testing, when I got back on it recently I found my tanks vary from 900 to 1100. So, been adding Mg to each tank at the same proportions. Two out of three tanks have been showing the same increase per day, as you would expect. However the third is not showing any increase. I've even doubled up the Mg dosing on that tank for a few days now and it remains steady at 900. Were it not for the other two tanks showing increases I would suspect the test kit or the supplement, but we can safely rule those possibilities out.

Is 900 maybe a sort of low water mark for the Elos Mg test kit? Ie., could it be that it's sub-900 but the test kit is unable to show a reading of less than 900?

Trying to think of other possibilities such as perhaps the Mg is simply being absorbed into the biology of the tank but it seems strange to me that the levels are flatlined instead of showing marginal increases or decreases. The resolution per drop on the test kit is 75 so it could be that it is increasing at very small increments and simply hasn't surpassed the threshold to read the next level (975) but again given that the other two tanks are increasing at roughly 75 per day and this tank's proportional additions are now twice that level, it just seems odd to me.

The resolution per drop is 75 on the Elos? Wow, that sucks. I think it's 5 or 10 on my Salifert. Have you double checked salinity and cal/alk?

That doesn't sound right? You're gonna be adding a LOT of drops to get to 1300-1400 then?? "two hundred and sixty three .. two hundred and sixty .. um .. four? Oh shize I just lost count!!!! One, two, three ...."

I have a Salifert Mg test kit too, now I'm going to go look at the instructions. It's been a while since I used that one because that one is a little fiddlier IIRC..

Salifert starts at something like 800 or...? I don't have it in front of me, but I'm SO sure that it has very small increments. Very strange that one tank isn't increasing Mg. Cal and Mg both interact with eachother though, so I would check your other parameters. Heck, i'd check all the other params...I do that anytime something seems funny and I usually find something else is off too.

Ah ok just checked, Salifert's resolution is 30 and I forgot you don't count drops but add drops and then compare the 0.01ml's strappings ..

I edited that one above like 50 times...lol. I'm bad for that. Oh, on second thought...oh and third thought...oh and 46th thought... :lol:

Salifert is 30? Huh...thought it was less than that, but still 30 is better than 75.

Elos is in increments of 50, my MG seems to drop pretty quick to if i don't monitor it and dose.

I guess if I have the Salifert test kit I can use it to see if I have a reading of <900 in that tank. Tomorrow.

Even still though, if it was, it's surprising because it's only a 40g so I do bigger water changes (percentage wise) and I've been using RBS salt which I thought was supposed to be the foshizzlenizzle or something. Seems disappointing to spend a premium on salt and then add Mg like it's going out of style to compensate for a low reading. And just in case anyone asks, I did pour the bag of salt into a bucket and shook it up for 5 minutes before using just in case it's a "you're not mixing your salt enough" type thing...

MY Elos is increments of 75. I hate it because the math isn't straightforward. It's a total afterthought too. The detailed instructions say 100, the inset card has a little sticker over the 100 that says 75. If I use 75 then I get a reading that matches the Salifert. To be honest I'm using the Elos because I want to use it up. I'm not a big fan of Elos with their this's and that's and their oops we really meant this not that but boy oh boy are we ever the best, pardon us for saying. Salifert is a little fussier but a) cheaper and b) a little more consistent from batch to batch??? At least has been in my experience.

You don't mix your salt for 24 hours? Maybe you aren't mixing good enough... :D

That's why I never bother with a premium salt. Every once in awhile I get lured in, and buy a bucket or two, but I always end up going back to the IO because I see no difference in my tank, and I don't find dosing to be very expensive. I worked it out that using (expensive) liquid supplements, supplementing an entire bucket of IO costs me less than $16.

Yeah, I got suckered again. I read post after post about how great a salt is and I think "I want to join this party! Please be my friend! I'm so lonely." It never works out. I kind of think a salt is just a salt. I dunno.

I've been fighting to get my CA, Alk, and Mag up for that past 2 weeks.. Dosing every night any numbers just won't increase to the numbers I want... I don't have a packed SPS tank, so I don't know where all this could be going..

03/24/2009 Ca: 380-390 Alk: 6.4 Mag: 1155
03/25/2009 Ca: 370-380 Alk: 6.4 Mag: 1260
03/27/2009 Ca: 370-380 Alk : 6.4 Mag: 1110 NO3: Undectable
03/29/2009 Ca: 330-340 Alk: 7.4 Mag: 1230
04/01/2009 Ca: 380-390 Alk: 6.7 Mag: 1260

Could it be going out the skimmer? How's your skimmate production? The skimmer on this tank needs to be emptied everyday whereas my other 2 it's only once per week.

It could be going out the skimmer if you are not dosing to make up what you throw out. The big assumption with doing regular water changes is that water changes will make up for what is lost,so if you had a fish only tank it would work out as long as the fish never drank any water. The water changes only,with a good salt, make the new water on par with natural salt water. It you do only a ,10-20% water change it does nothing for the other 80-90% so every day our values become less and less. Unless we dose or do 100% water changes we will never win.

But I AM dosing right now, ie. not relying on water changes. I've gone through nearly a whole bottle of Mg so far this week and it's flatlined at 900. That's why I think it's odd? Why would the number not be going up at all. I'm using Tailored Aquatics Mg. 2 out of 3 tanks (with much heavier bioloads) are increasing, the one is not. Is there anything to watch out for that could be interfering with Mg or Mg testing?

Are calcium and alk up to par? Maybe take a cup of that tank water and see if you can get Mg up in that cup.

ok, need some more info ont he tanks, what is in the ones that are good and what is in the one that is bad? (coral wise) also is there a sand bed in each tank and is it the same in each tank. are your Ca and alk the same in all 3 tanks? oh and is the low tank a new tank?

don't worry about the 24 hour mixing, as long as you are mixing it good it won't make a differance like that. and as long as it is mixed to the desolving poing it doesn't matter if it is 5 min or 5 days. once it is desolved it is desolved. I mix for 5 min with my drill propeller and then let the mag drive go for another hour. but after the 5 min with the propeller it is good.

I found DSB are good for sucking Mg out of the water. never had 1/2 the work to keep up Mg when I went bare bottom.

Steve

Ok sorry, I meant mix the salt itself, not the water with salt in it. I once complained about another premium salt brand that was reputed to have Mg at 1400, but when I tested Mg, it was 900. (I'm actually really starting to wonder if the problem is Elos can't tell me if Mg is <900 - it clamps at 900 - just on account I've never had a reading less than 900). Anyhow, I ranted about it, and one thing that came out of those conversations was that you're supposed to mix salt before you use it. For real. Isn't that the lamest thing? But I guess if they're adding this and that when they're making the salt up, the proportions may be all correct as far as the total batch is concerned but the dispersal may not be as homogenous as one would like. :neutral:

Tank with the flatlined Mg is not new and has no sand. It has maybe a half dozen 1" SPS frags, two smaller colonies, a bubble coral, a gigantea carpet and two ocellaris. Maybe about 3 billion aiptasia though. It's a 24x24x12 shallow lagoonal thing.

Ca is 360, Alk is 7 and Mg is 900.

The other tanks have similar but different readings. One has Ca 420, Alk 7 and Mg 1100 (as of last night anyhow, I am still raising it though), the other has Ca 370, Alk 7, and Mg 1050 (also still being raised). One other is a BB tank, and the last one has a 1" skiff of sand.

I am betting dollars to donuts now that the issue is in fact the test kit can't tell me a number less than 900. I will test tonight with Salifert and see what shakes out.

If the salinity levels are the same I am with you on the test kit.

no reason for excessive Mg consumption in your tanks.

Steve

Salifert says 1005, Elos still says 900 tonight. :neutral:

I was wrong about Salifert resolution at 30, it's 30 units apart on the lookup sheet but going up in 0.02ml increments. So it's really 15.

I also dropped the vial for the Elos test kit and shattered it into about a billion little shards. Yay me. Man those things break super easy.

Hmmm...that's interesting that the two kits are so far off from eachother. I "hate" it when that happens. Could it be that the kits are only off by like 30 or 40 from eachother, but because the Elos jumps by 75 per drop it's showing 105 off?

Yeah, I'm not too pleased with the disparate readings. I don't think I've ever had the two read exactly the same but it's never been this far apart. I wonder which one is slipping. Ugh, I hate test kits. Although at least they give me a rough ballpark if nothing else.

So I've confirmed now that Elos simply can't tell you anything less than 900.

And I've confirmed that my RBS salt has very low Mg at 825.

Ugh, well, at least that mystery is solved.

So i guess we are now back to a question:
What is the best reef salt out there:question::question::question:

IO :mrgreen:

Steve

Ah, sorry no IO for me:
To much dirt and still need to supplement, this means more testing, more time and more money involved.

I love IO.....

so much so that I've even made my own song IO IO it's off to the salty shops I go.......:lol:

I've been using it from the day I started and will until the day I stop reefing, adding abit of Ca and Mg costs pennies compared to spending $20 more per bucket.

Too much dirt? Say what?

To quote myself:
Plus, if you use cheaper additives (which would be smart!) it could cost 1/4 of what it costs me to supplement the IO.

what dirt? 7 years of using IO I have never seen any dirt.
and all you need to do is bump up Ca a tiny bit.. 360 to 380 isn't much.. I just let my Ca reactor do it.

Oh and did I mention in those 7 years, I never had any salt related problems either:mrgreen:

Steve

why are you increasing Ca if you are getting a NSW level of 380?

Steve

I'm kind of apprehensive about the future of IO with the chapter-11/receivership/whatever of Aquarium Systems/Spectrum Brands/whatever-they're-called. From all I've been able to read though, for now and the foreseeable future, they intend to keep operating. Hope that they are able to resolve and continue, because it would truly suck if IO went away. :(

I ran with IO for many years early on in the hobby and yeah, never had a problem with it. Only switched because I wanted to see why there were so many other options but at the end of the day, any lesson I've learned is that a salt is just a salt. It is a commodity item.

Let's face it, you have to dose stuff anyhow, and you have to test stuff anyhow, no matter what. Maybe with one salt or another you may have to dose more of this or less of that but you're not doing any less testing, ultimately if you do you're taking a risk (this is a lesson I seem to need to relearn every 6 months or so :redface: ).

I'm pretty sure I'm "coming home" to IO for the next little while...

For IO, anyone know what the average Mag level is? Roughly.

Usually it is around 1270-90, but my new bucket is 1170. Usually the Calcium is 360-370, but my new bucket is 400. Alk is always around 11-12 dKH. This is the first "off" bucket I ever had. I don't care...I test every new bucket anyway. :)

Sorry, I bolded my mistake. When I test IO it's usually 360-370. I just looked at my recordings. My quote was wrong.

Where do you get that number from? Randy Holmes Farley always writes that NSW around the world averages 410 ppm.

It is known that calcium levels of 360 and under start to inhibit growth of stony corals. I don't have a calcium reactor, so I rely on dosing. It is easy for my tank to drop 20 ppm calcium between dosing (mostly because my tank sitter isn't very good at dosing often enough, which is annoying, but at least she does it), so it's too risky for me to be at 380 ppm. I dose my tank to be 415-425 ppm, but as long as it's at or over 400 I'm happy.

WOW, Mg at 1100(ish)... LOL. It's so nice and high! :lol: I'd only need to add a LITTLE Mg as opposed to .. the entire $#@$#@! bottle!

I know what you're talking about with respect to the "dirt". However, IO isn't alone on this problem - I've seen black sediment and particulate in Kent, Instant Ocean, Reef Crystals, and Seachem Reef Salt over the last year or so of switching between salt brands.

BTW have you guys herd that as per SeaChem, all liquid additives are contaminated with ammonia(!)?
i wonder if that is true?
quote: Reef Advantage Magnesium contains no ammonia! This is a common contaminant in every liquid magnesium supplement on the market.end quote
http://www.jlaquatics.com/product/sc...+600+Gram.html

I have heard this as well as nitrates. I'm not sure if it's true though.

So, just updating this thread with additional observations:

1) (And just to echo what's already been said in a couple other threads lately) I can't beleive how much Mg it takes to raise Mg in the tank. I ordered 20 lbs from Chemmaster and I've used up 4 lbs in the last TWO WEEKS. :eek: (Over 3 tanks and in new water change water mind you.)

2) I've used up my Elos test kit and am now finishing up my Salifert. One thing I am finding with the Salifert .. and I'm not sure if this is an artifact of: 1) the age of the test kit (about 1 year or so), or 2) the Salifert Mg test kit in general, or 3) normal day to day fluctuations of Mg in solution,or 4) maybe I suck at using test kits ... but I can't beleive how inconsistently my tanks' Mg levels are from day to day. For example, I was targetting 1400 and I was adding Mg at certain amounts and testing each day. So say I wanted to raise Mg by 50 per day, I would try to find the amount that would do this. But the same amount of additive would never raise the levels by the same amount. And off by factors of 3 or 4 in some cases. Ie., one day, 15ml would raise a tank 15, but another day, 15ml would raise a tank by 45..or 135. :eek: HUH?? ... Also noted that the amount from tank to tank was not directly proportional to water volume (ie., my 40g took an amount that was not anywhere near twice that what was for the 20g, and the 115g took even more proportionally. It's like it's by "water volume squared" maybe?) Weird??? Even weirder, my 110g was the first to hit 1400. So I stopped adding Mg because now I'm shifting from "raise Mg" into "maintain Mg" (and for that I want to determine what the consumption rate is on, say, a weekly basis, then I'd find out how much it takes to replenish that amount, divide by 7 and hey presto, there's the amount to dose each day). But the next day, without adding any Mg, the Mg level had jumped 30 on its own.

Me confoozled by this. :redface:

I find the test kits resolution is very low as well.

I just aim for 1300 to 1450 (maybe even 1500), as long as it is in that range I am happy.