dosing magnesium

[Sea Turtle]

I bought the bulk reef supply magnesium two part mixture and the bottle with pump. On average, how much of that should I be squirting in the tank per week? I have a 75 gallon tank. Should this be something that I should be dosing once a day?

 

[Len]

There's no formula. You get your Ca and alk to the desired levels, then you figure out how much to dose each day to maintain those levels through testing (trial and error). There are some suggested starting points (for example, for sps tanks, 1ml/gallon/day is what's recommended), but you need to test and retest to get it dialed right. After that's set, then you add the magnesium portion to get it to your desired levels, and then you start doing the same trial and error testing to maintain the Mg levels. I automate my dosing for the Ca and alk, but I will manually add Mg on a weekly or even a monthly basis depending on my test results. I use BRS' calculator to figure out how much Mg should be added before I add it.

 

[Sea Turtle]

There's no formula. You get your Ca and alk to the desired levels, then you figure out how much to dose each day to maintain those levels through testing (trial and error). There are some suggested starting points (for example, for sps tanks, 1ml/gallon/day is what's recommended), but you need to test and retest to get it dialed right. After that's set, then you add the magnesium portion to get it to your desired levels, and then you start doing the same trial and error testing to maintain the Mg levels. I automate my dosing for the Ca and alk, but I will manually add Mg on a weekly or even a monthly basis depending on my test results. I use BRS' calculator to figure out how much Mg should be added before I add it.

Ok, that sound more like it. I do automatically dose alk and calcium. Just started manually adding Magnesium and it seems to be at 1500ppm and not coming down. Wasn;t sure if I was doing it properly. I guess that is something that I will only have to squirt in once every week or two.

 

[Len]

There's no formula. You get your Ca and alk to the desired levels, then you figure out how much to dose each day to maintain those levels through testing (trial and error). There are some suggested starting points (for example, for sps tanks, 1ml/gallon/day is what's recommended), but you need to test and retest to get it dialed right. After that's set, then you add the magnesium portion to get it to your desired levels, and then you start doing the same trial and error testing to maintain the Mg levels. I automate my dosing for the Ca and alk, but I will manually add Mg on a weekly or even a monthly basis depending on my test results. I use BRS' calculator to figure out how much Mg should be added before I add it.

Ok, that sound more like it. I do automatically dose alk and calcium. Just started manually adding Magnesium and it seems to be at 1500ppm and not coming down. Wasn;t sure if I was doing it properly. I guess that is something that I will only have to squirt in once every week or two.

Yeah. You don't add Mg at anywhere near the same pace as the Ca/Alk portions. I think one reason why some people don't automate the Mg portion it doesn't seem to depreciate at a linear rate like Ca and alk. If I test my Mg and it's fine, I simply don't dose any.

 

[Sea Turtle]

Do I need to be concerned with elevated Magnesium reading such as 1500-1600ppm?

 

[Anonymous]

Do I need to be concerned with elevated Magnesium reading such as 1500-1600ppm?

Very likely not, though I'd be curious to see how it got that high in the first place. Have you double-checked your test results? Those Mg tests can be very finicky.

 

[skyfreak73]

Those Mg tests can be very finicky.

Especially the ELOS kits, in my experience! I highly recommend the Seachem Reef Status Mg kit. It includes a reference sample to check the accuracy of the reagents.

 

[Anonymous]

FWIW I use this method:

http://reefkeeping.com/issues/2006-02/rhf/index.php

With the aid of this on line calculator

http://home.comcast.net/~jdieck1/chemcalc.html

IME it can take what seems to be a very large amount of magnesium especially after a tank has ran for some time. my 55g for instance was at 700-800 ppm magnesium and required 2-4 pounds of epsom salts to get it up to 1350ppm.

just my .02

 

[Sea Turtle]

Those Mg tests can be very finicky.

Especially the ELOS kits, in my experience! I highly recommend the Seachem Reef Status Mg kit. It includes a reference sample to check the accuracy of the reagents.

Yes, I use teh ELOS kits as well and I am a little unsure as to how acurate they are. Sometimes I get 1350 and then the next day I will get 1500ppm. I don;t think I like ELOS.

 

[Sea Turtle]

I have another question regarding the measuring of the magnesium.

ELOS is refering the mg/Lt. (36-6 drops=1.500 mg/Lt. of magnesium). Is this 1500? Am I using this test kit correctly?

 

[skyfreak73]

ELOS is refering the mg/Lt. (36-6 drops=1.500 mg/Lt. of magnesium). Is this 1500? Am I using this test kit correctly?

Yes, it would appear so. However, I'll repeat that in my experience, the ELOS test kits are unreliable. I kept reading 900 on my kit after heavy supplementation, but when I took a sample in to my LFS, they tested it with another ELOS kit and it showed 1200 the same day. From that moment, I swore off the ELOS kits.

The Seachem Reef Status kit is the most accurate hobbyist kit on the market. You'd have to use a calibrated electronic meter or GC/MS to get more accurate.

 

[Sea Turtle]

ELOS is refering the mg/Lt. (36-6 drops=1.500 mg/Lt. of magnesium). Is this 1500? Am I using this test kit correctly?

Yes, it would appear so. However, I'll repeat that in my experience, the ELOS test kits are unreliable. I kept reading 900 on my kit after heavy supplementation, but when I took a sample in to my LFS, they tested it with another ELOS kit and it showed 1200 the same day. From that moment, I swore off the ELOS kits.

The Seachem Reef Status kit is the most accurate hobbyist kit on the market. You'd have to use a calibrated electronic meter or GC/MS to get more accurate.

Hmmmm, this was very similar to what I went through. I took some water to the lfs, he said my Mg was at 1100ppm. So I knew that I had an issue and I bought an ELOS test kit from him. I got home and tested the water... it was 1300ppm. Also, I have found that the regiment droper on phase 2 dosent;t measure droplets cosistently. Some are bubbles/half drops. I'm done with it.

 

[Anonymous]

ELOS is refering the mg/Lt. (36-6 drops=1.500 mg/Lt. of magnesium). Is this 1500? Am I using this test kit correctly?

Yes, it would appear so. However, I'll repeat that in my experience, the ELOS test kits are unreliable. I kept reading 900 on my kit after heavy supplementation, but when I took a sample in to my LFS, they tested it with another ELOS kit and it showed 1200 the same day. From that moment, I swore off the ELOS kits.

That can happen with any test kit with different operators. It would have been interesting to see what the LFS number would have been had they tested it with your test kit. More importantly, why believe that the LFS is is right and your was wrong - because the number seemed better? People only seem to retest when the don't like the number, but it seems that the tests would be equally as incorrect even when the number is what you liked.

The Seachem Reef Status kit is the most accurate hobbyist kit on the market.

What are you basing that on?

You'd have to use a calibrated electronic meter or GC/MS to get more accurate.

I don't believe that is true. We used those methods at work and the test still show a wide variability.

I think test kits are really only good for trending, not for actual numbers, which is why such a wide sweet spot for most parameters is suggested. I also thik the trending is only accurate if the same person does the test every time because of the inherent variability in the testing methods

So, for the OP, test, then test the next week, then add 1/2 the Mg of what you calculate needs to be added, then test again the next week. Shoot for between 1280 and 1350 (1400).

 

[skyfreak73]

More importantly, why believe that the LFS is is right and your was wrong - because the number seemed better? People only seem to retest when the don't like the number, but it seems that the tests would be equally as incorrect even when the number is what you liked.

I didn't say that I accepted one set of values over another...you assumed that I accepted the higher number because I found it more favorable. I operated on the assumption that both operators (myself and the person at my LFS) followed the test directions accurately and therefore found the fault with the test kit. I didn't accept anyone's numbers at that point since we both used the ELOS test kits.

What are you basing that on?

Experience. If you've found another hobbyist kit more accurate, please inform.

 

[Anonymous]

More importantly, why believe that the LFS is is right and your was wrong - because the number seemed better? People only seem to retest when the don't like the number, but it seems that the tests would be equally as incorrect even when the number is what you liked.

I didn't say that I accepted one set of values over another...you assumed that I accepted the higher number because I found it more favorable.

Gotcha. You ditched Elos because different people got different numbers. I don't think that has anything to do with Elos - different operators will almost always get different numbers, even when using the same brand of test kit.

I operated on the assumption that both operators (myself and the person at my LFS) followed the test directions accurately and therefore found the fault with the test kit.

Not a good assumption. When doing any tests to compare products, at the very least the same person needs to do the testing due to all the variables in the testing method. Operator 'error' is one of the biggest impacts on test results.

I didn't accept anyone's numbers at that point since we both used the ELOS test kits.

But again, different operators get different numbers. Happens all the time. I don't think that is necessarily a good reason to dismiss a brand of test kit.

What are you basing that on?

Experience.

Ah - so its not that Seachem is the most accurate kit on the market like you said, you mean that you like the kit. I think these differences are important because the first way you said it made it seem like there had been some kind of independent testing that made a determination about what was 'best'.

If you've found another hobbyist kit more accurate, please inform.

I think I covered this already - I don't find any of them to be particularly accurate, but they are useful for trending.

 

[skyfreak73]

Let's see if this horse still has a bit of breath left in her...

Ah - so its not that Seachem is the most accurate kit on the market like you said, you mean that you like the kit. I think these differences are important because the first way you said it made it seem like there had been some kind of independent testing that made a determination about what was 'best'.

Actually, I meant exactly what I said: the most accurate. I thought the fact that I like the kit went without saying. I say the most accurate simply because of the titration method used. With any of the titration kits that I've used, including ELOS, the titrant drops dose at a fixed size with no reliable way to measure partial drops. Since the Seachem kit uses a titration syringe, the operator (presumably human and therefore yes, prone to error) can measure more accurately. I find this accuracy particularly helpful in trending, particularly when trending the daily consumption of alkalinity, calcium, magnesium, etc...for the purpose of determining a daily dose of supplements to keep the reef parameters at desirable levels.

 

[Anonymous]

The Seachem Reef Status kit is not the most accurate hobbyist kit on the market - there has been no testing done to make this determination. There are plenty of other kits that use titration syringes for greater accuracy in measuring titrant drops.

 

[skyfreak73]

Please do inform us on these "plenty of other" hobbyist test kits for Mg that use a titration syringe.

 

[Anonymous]

You seem to be taking this personally, which seems strange to me. This is a discussion, not a fight - isn't it? I am sorry if I have somehow offended you and that was not my intent.

Salifert and lamotte tests kits use a syringe.
FWIW, I like the elos test kits because they do not use a syringe (way more potential for operator error with a syringe) and have found them to be comprable to the expensive equipment at work.

 

[skyfreak73]

You seem to be taking this personally, which seems strange to me. This is a discussion, not a fight - isn't it? I am sorry if I have somehow offended you and that was not my intent.

No offense taken...I genuinely want to learn and presume others do as well (apologies for speaking on behalf of said 'others').

Salifert and lamotte tests kits use a syringe.

Great information; I may give the Salifert a try since it seems more economical than the Seachem Reef Status.

FWIW, I like the elos test kits because they do not use a syringe (way more potential for operator error with a syringe) and have found them to be comprable to the expensive equipment at work.

If I were offered a stick at a fixed length that has one mark right at the midpoint, dividing the length of the stick in two, then offered another stick at that same fixed length that has 10 marks on it dividing the length of the stick in ten, I would think I could make more accurate measurements with the stick that has 10 marks on it.

It seems to come down to a "good enough" position: if the stick with one mark on it can make 'good enough' measurements for someone to do something useful with, it would seem that the stick with 10 marks may offer more opportunity for error in measurement.