Magnesium usage

[Jrod381]

Another comment that might help you make your reef disaster resistant. In addition to the usual back-up equipment like extra pumps, heaters, salt, always keeping 50 gallons of RODI on hand, etc.., you might want to consider a small generator, and a small plug-in window air conditioner. The little camping generators that are available from the B.O.R.G. (big orange retail giant) cost about $450. A far more reliable and quiet version is available from Honda. Either way, they've saved my tanks on multiple occasions. Ditto for the window AC - cost me $150, is small and light enough to hoist into a window with little trouble,

Yea I live in Florida so I have A 7500watt generator. I just picked up a small 6000btu ac right after that happened. Wife said you care more about the tank than me lol.

 

[Dkeller_nc]

Ha! I don't know about that - despite being a Southerner, I can't stand hot weather. I lived in a house without A/C for the better part of 10 years during grad school and afterward, and sleeping at night even with a fan blowing on you the entire time really blows. That AC that saves the tank should would be nice to put a cot in front of....

 

[DeputyDog95]

My tank seems to consume more Mg than most on here. It is an SPS-only tank though if that makes a difference.

Right now, based on Red Sea's liquid dosing numbers, I'm consuming about 3ppm of Mg/day and dosing 17ml/day to stay over 1325ppm. Seems weird as Red Sea's "reef recipe" calls for about a third of that (6ml) to hit 1280ppm.

I'm kind shocked to read that some people are consuming that or less per week.

And the measurement I'm taking is likely a little low, as the ICP always shows the Mg level to be at least 30-50ppm above my Salifert testing.

Weird.

 

[Randy Holmes-Farley Verified Community Expert]

My tank seems to consume more Mg than most on here. It is an SPS-only tank though if that makes a difference.

Right now, based on Red Sea's liquid dosing numbers, I'm consuming about 3ppm of Mg/day and dosing 17ml/day to stay over 1325ppm. Seems weird as Red Sea's "reef recipe" calls for about a third of that (6ml) to hit 1280ppm.

I'm kind shocked to read that some people are consuming that or less per week.

And the measurement I'm taking is likely a little low, as the ICP always shows the Mg level to be at least 30-50ppm above my Salifert testing.

Weird.

Coraline algae is proportionally the biggest user of magnesium in a reef tank, and it will consume about 1/10th as much magnesium as calcium.

 

[DeputyDog95]

Coraline algae is proportionally the biggest user of magnesium in a reef tank, and it will consume about 1/10th as much magnesium as calcium.

Thanks for the quick reply.

I guess if I pretended that the Red Sea Alk and Ca liquids were a 1 to 1 (they're 1 to 3, the Ca is concentrated), that would put me at 6ml per day of Mg since I'm dosing 60ml of Alk and presumably under typical circumstances 60ml of Ca (only actually 20ml in my case). I'm almost triple that to maintain 1330-1335ppm Mg in my tank.

It is only SPS and there is quite a bit of coralline.

Is that possible? Seems really high compared to most... My testing seems to be ok and is co-witnessed by the ICP.

 

[Randy Holmes-Farley Verified Community Expert]

Thanks for the quick reply.

I guess if I pretended that the Red Sea Alk and Ca liquids were a 1 to 1 (they're 1 to 3, the Ca is concentrated), that would put me at 6ml per day of Mg since I'm dosing 60ml of Alk and presumably under typical circumstances 60ml of Ca (only actually 20ml in my case). I'm almost triple that to maintain 1330-1335ppm Mg in my tank.

It is only SPS and there is quite a bit of coralline.

Is that possible? Seems really high compared to most... My testing seems to be ok and is co-witnessed by the ICP.

Can you run those through a calculator like the one below to compare ppm per day?

Reef Chemistry Calculator

 

[DeputyDog95]

Can you run those through a calculator like the one below to compare ppm per day?

Reef Chemistry Calculator

Not sure... This calculator seems to be better at telling you how to "dose up" if I'm looking at it correctly.

I've been working off RS's Mg instructions to figure out my consumption by how much liquid I'm dosing. I'm holding steady at 1335ppm dosing about 17ml per day.

Concentration:​

Liquid supplement: 1ml will raise the Mg level of 100 liters (25 gal) by 1ppm.

Powder supplement: 1g will raise the Mg level of 100 liters (25 gal) 1.34ppm.
1 kg will make 1.7L of stock solution.

 

[DeputyDog95]

I just made fresh batch of Red Sea Blue Bucket and mixed it to 35ppt. According to the bucket, it should be 1280ppm at 35ppt. I tested the Mg with my Saliftert kit and it came in at 1275. So my Mg kit appears to be pretty close.

I guess I just have high Mg consumption for whatever reason...

 

[Randy Holmes-Farley Verified Community Expert]

Not sure... This calculator seems to be better at telling you how to "dose up" if I'm looking at it correctly.

I've been working off RS's Mg instructions to figure out my consumption by how much liquid I'm dosing. I'm holding steady at 1335ppm dosing about 17ml per day.

Concentration:​

Liquid supplement: 1ml will raise the Mg level of 100 liters (25 gal) by 1ppm.

Powder supplement: 1g will raise the Mg level of 100 liters (25 gal) 1.34ppm.
1 kg will make 1.7L of stock solution.

I just want to know, before commenting, how many ppm per day we are talking about. Especially for unbalanced additives like Red Sea, talking in ml is just confusing.

 

[Randy Holmes-Farley Verified Community Expert]

I just made fresh batch of Red Sea Blue Bucket and mixed it to 35ppt. According to the bucket, it should be 1280ppm at 35ppt. I tested the Mg with my Saliftert kit and it came in at 1275. So my Mg kit appears to be pretty close.

I guess I just have high Mg consumption for whatever reason...

Msybe, but no one Has more demand than about 1/10th of the calcium demand. There’s no secret sink for magnesium.

 

[DeputyDog95]

I just want to know, before commenting, how many ppm per day we are talking about. Especially for unbalanced additives like Red Sea, talking in ml is just confusing.

Based on my rough calculations using Red Sea's formula for consumption...

The total tank/sump volume is 500 liters or about 132 gallons. I'm going with a net volume of 125 gallons for easy math.

I'm currently dosing 17ml/day, which should be the ballpark consumption equivalent of about 3.4ppm/day.

Red Sea Liquid Mg instructions:

Concentration:​

Liquid supplement: 1ml will raise the Mg level of 100 liters (25 gal) by 1ppm.

Going with my tank having a volume of 125g, every 5ml should raise the Mg by 1ppm. 17ml/day divided by 5ml is 3.4ppm per day.

Or am I botching the math?

​

 

[DeputyDog95]

Msybe, but no one Has more demand than about 1/10th of the calcium demand. There’s no secret sink for magnesium.

Yeah, not sure what to make of that. Doesn't seem right, but that's what's happening.

Even Red Sea's "reef recipe" calls for less Mg that what I'm doing. Despite that I am running about 50ppm higher than their recipe, consumption should the same regardless.

Oddly enough, My Ca and Alk land very close to their projected number as I'm currently dosing 60ml/Alk and 20ml/Ca.

As mentioned before, I tested a fresh batch of water with my Saliftert kit and it was very close to the what the projected Mg should be at 35ppt. I've tested Alk at 35ppt before as well, and that came in close too so I feel reasonably confident on my testing and the ICP's.

Even the RS recipe for Mg appears to be about 10% of the Alk, which under normal circumstances with most two parts, would also be 10% of the Ca as you suggested.

I did recently calibrate the doser and it's spot on.

Very weird.

 

[DeputyDog95]

So I think I figured out my unusual Mg consumption...

I had another ICP test done. Not only was my salinity over a point low, my Salifert test kit is consistently reading around 55ppm low.

Now that I've slowly adjusted my salinity up to 35ppt and am interpreting my Salifert results as 55ppm low than they really are, I was perfectly fine with the recommended Red Sea dosage. Which is basically the equivalent of around 1-2ppm consumption per day. So now I have actually have high Mg ( around 1450ppm), a big part due to the salinity increase. Interesting what an effect salinity has on the tank's elements. You can literally see a before and after difference.

I've turned Mg off for now and will just let it come back down on it's own and through water changes. I had a feeling something was off. Mystery solved.

 

[Randy Holmes-Farley Verified Community Expert]

So I think I figured out my unusual Mg consumption...

I had another ICP test done. Not only was my salinity over a point low, my Salifert test kit is consistently reading around 55ppm low.

Now that I've slowly adjusted my salinity up to 35ppt and am interpreting my Salifert results as 55ppm low than they really are, I was perfectly fine with the recommended Red Sea dosage. Which is basically the equivalent of around 1-2ppm consumption per day. So now I have actually have high Mg ( around 1450ppm), a big part due to the salinity increase. Interesting what an effect salinity has on the tank's elements. You can literally see a before and after difference.

I've turned Mg off for now and will just let it come back down on it's own and through water changes. I had a feeling something was off. Mystery solved.

Thanks for the update!