View Full Version : really high Mg? >1600

06/06/2014, 06:32 PM
So I finally broke down and bought a dosing pump (fish street) and some BRS 2 part, and a red sea Reef Foundation pro test Kit.

I'd been using Seachem Reef Complete and Reef Carbonate just following the basic instructions, adding about 15ml 3x a week to my 60g reef system...things have been ok (mostly) for several years with that system but I was growing tired of manually dosing.

So before I set up the dosing I did my tests. I've never tested magnesium in my tank and I am kind of surprised by what I tested at.

According to the Red Sea kit I am at 1680ppm Mg. I guess Reef Complete has mag in it, but why should it be so out of whack? (A second test changed at about the same point, maybe 1660ppm)

So I have:

Ca 460
KH 7.6
Mg 1680

should that be a concern, can I get things back on track with 2 part, will a sharp drop in Mg from a 20% wc harm anything?

Right now the tank is mostly softies with a medium sized Duncan and some random acro frags, but no clams or big SPS colonies.

thanks for any advice or comments in advance!


06/06/2014, 09:18 PM
so I missed another post about this today: http://www.reefcentral.com/forums/showthread.php?t=2416444

The Red Sea kit Mg test is bunk?

06/06/2014, 10:07 PM
My Red Sea Mg matches my Salifert Mg if you follow the instructions exactly (which are a bit cumbersome).

Nice video here: http://m.youtube.com/watch?v=MofaqM-I6uM

06/06/2014, 11:20 PM
What salt do you use? Oceanic, for example, contains pretty high Mg.

I've had mine up to 1700 or 1800 with no ill effects. Some people drive it up higher than that when using Tech M to kill bryopsis.

Randy Holmes-Farley
06/07/2014, 06:51 AM
If you are using a Red Sea kit to get that value, then it might be the kit, but yes, knowing what salt mix would also help figure out if it is real or not. :)

06/07/2014, 11:30 AM
I use IO Reef Crystals but I haven't done a WC in about 6-7 weeks.

06/07/2014, 11:52 AM
My Red Sea Mg matches my Salifert Mg if you follow the instructions exactly (which are a bit cumbersome).

Nice video here: http://m.youtube.com/watch?v=MofaqM-I6uM

Thank you hilgert! After watching the video I retested and watched for the blue flash, THAT happened at .68ml, so 1360ppm which is more in line with what I would expect...

Also thank you Randy for just being so quick to assist when we have questions :)

Randy Holmes-Farley
06/07/2014, 12:12 PM

Happy Reefing. :)

06/07/2014, 09:10 PM
Just to be sure, this evening I did another cross check with my Red Sea Mg kit (following the instructions *exactly*) and two Salifert Mg kits (one in-date, one just expired), and got similar readings (as expected).

I then did a "rushed" test (not waiting 15 seconds to swirl each drop) with the Red Sea kit and got the "1600 result". Interestingly, when I did the same (rush) with the Salifert kit I got a reading consistent (within what I'd call a reasonable amount) with the prior (non-rushed) Salifert reading.

But, the Red Sea Mg kit is less expensive than the Salifert kit if you get it as part of the Big Three kit, and unlike Salifert you can buy refills for the Red Sea kits.

06/07/2014, 09:29 PM
I'm thinking high mag levels don't hurt anything if it is raised gradually. Lots of people get rid of bryopsis by raising mag up to 1800 without problems. Can someone confirm?

Randy Holmes-Farley
06/08/2014, 05:19 AM
I wouldn't recommend maintaining magnesium that high since, yes, some people do report problems when doing the bryopsis kill experiment (snails immobile, etc), although one cannot know if those problems are due to the magnesium or impurities in the magnesium additive (or possibly even coincidence).

FWIW, it seems very unlikely to me from first principles that commercial magnesium supplements are magically able to kill bryopsis and not harm any other creature that reefers maintain.