Dosing Mag?

[FL_Reefer]

I have a dosing question. My tank has been using 2.8dkh of Alk and 20ppm of Cal every 2 weeks. My dosing has been keeping up with the amounts used but my question is about Mag. I haven't been dosing any Mag at this time. I do a water change every 2 weeks with Red Sea regular salt about 15%. My tank is a 60gallon cube with 55 gallons TWV. My problem is that the Red Sea Test kits have a good amount between numbers and really can't figure out how much Mag is being used. Randy can you tell me how many ppm of Mag I should be dosing in this 2 week time frame?

 

[Ryengoth]

What are your ca and mg readings before you dose and 24hr after you dose?

 

[FL_Reefer]

Before:
Alk:7.8 dkh
Cal: 418 ppm
After:
Alk: 8dkh
Cal: 420 ppm
Mag is unknown due to the Red Sea Test kit number span. I believe there is a 80ppm between test levels if you know what I'm talking about.

 

[Ryengoth]

IMO, that's such a low level of ca, it's going to be hard to monitor the mg swing. Ca and Mg are ionic partners so I'd dose Mg equally (or at least 50%) and see if your Mg levels start to increase across 3 or 4 dosings. I doubt you'll have ca precipitate at the low amount of mg change if the soup is saturated. I'd love to hear input from some seasoned reef owners, though.

 

[FL_Reefer]

Thank you for your response! I was dosing 50% of my Cal at one time but stopped a couple of months ago. My Cal and Alk have been stable with my dosing now. I have added quite a few acros lately so I wanted to get ahead of this before the uptake started to increase. Thanks again and I'm open to anyone else's opinion too

 

[Randy Holmes-Farley Verified Community Expert]

For a 20 ppm of calcium decline, magnesium will decline 2 ppm or less, sometimes a lot less (depending on the coral types you keep).

So I doubt you have to think about adding any since regular Red Sea salt mix (at 35 ppt) has enough magnesium ( about 1300 ppm) to account for some small loses, especially with water changes.

FWIW, magneisum supplementation is not the only reason to use a magnesium supplement with a DIY two part of calcioum and alkalinity (sulfate additions are important too), but in this case you are not adding enough of the two part to worry about nedign to add sulfate.

 

[Ryengoth]

How consistent is Red Sea mix? I've read about and heard of inconsistencies with Reef Crystals. I choose to mix and dose separately due to that.

 

[FL_Reefer]

Ok thank you Randy and that was what I was thinking as well about my water changes keeping up with the small amount that was being used. I appreciate it and thanks again!

 

[FL_Reefer]

In my experience, and my opinion Red Sea Mixes the same every time. I'm sure there is little differences between batches (mixers errors) but all in all it is the only salt I use. Just my preference though.

 

[Randy Holmes-Farley Verified Community Expert]

How consistent is Red Sea mix? I've read about and heard of inconsistencies with Reef Crystals. I choose to mix and dose separately due to that.

IMO, most of the comments about inconsistencies are due to one of two things: people using a partial bag or bucket that separated during shipping, or testing error.

People get all sorts of test results that are simply impossible (like magnesium in their tank dropping 100 ppm in 2 days), and if they did those same tests on new salt mix rather than their tank, they'd blame the salt, when it isn't the case.

 

[Randy Holmes-Farley Verified Community Expert]

Ok thank you Randy and that was what I was thinking as well about my water changes keeping up with the small amount that was being used. I appreciate it and thanks again!

You're welcome.

Happy Reefing.

 

[FL_Reefer]

IMO, most of the comments about inconsistencies are due to one of two things: people using a partial bag or bucket that separated during shipping, or testing error.

People get all sorts of test results that are simply impossible (like magnesium in their tank dropping 100 ppm in 2 days), and if they did those same tests on new salt mix rather than their tank, they'd blame the salt, when it isn't the case.

I agree completely Randy

 

[JimWelsh]

IMO, most of the comments about inconsistencies are due to one of two things: people using a partial bag or bucket that separated during shipping, or testing error.

I did experience one bag of regular Instant Ocean that had relatively high Mg (over 1700 PPM). Of course, my encounter with this bag coincided with the purchase of a new Mg test kit, and so I contacted the vendor and demanded a replacement test kit. It was only after the replacement test kit arrived and gave the same result that I came to the conclusion that the issue was with the salt. Yes, I do always make sure to mix the bag contents as much as possible before using.

 

[Randy Holmes-Farley Verified Community Expert]

I did experience one bag of regular Instant Ocean that had relatively high Mg (over 1700 PPM). Of course, my encounter with this bag coincided with the purchase of a new Mg test kit, and so I contacted the vendor and demanded a replacement test kit. It was only after the replacement test kit arrived and gave the same result that I came to the conclusion that the issue was with the salt. Yes, I do always make sure to mix the bag contents as much as possible before using.

Thanks, Jim. I don't doubt there are off batches of salt around. I just do not think it as common as many people claim.

 

[black_art]

Dear Randy
In my country Magnesium Sulfate ( Epsom Salt ) is a little expensive so is it possible to use Magnasium Chloride Hexahydrate to increase Mg in reef tank instead of Epsom Salt?
Regards

 

[Randy Holmes-Farley Verified Community Expert]

Yes, and if you can only pick one, magnesium chloride is the one to use.

 

[black_art]

Thank you for your reply. There are two type of Magnesium Chloride: first type is used in industries which is 5$ per Kg and second one is used in laboratory which is 30$ per Kg. Thus, is it possible to use industrial grade?

 

[Randy Holmes-Farley Verified Community Expert]

Thank you for your reply. There are two type of Magnesium Chloride: first type is used in industries which is 5$ per Kg and second one is used in laboratory which is 30$ per Kg. Thus, is it possible to use industrial grade?

Do you know who makes them?

One issue with magnesium chloride is potential ammonia impurity.