Dosing magnesium

asylumdown · #1 05-16-2013, 06:46 AM

Ok ok, I know I'm supposed to know this and shame on me for not spending 45 minutes on google figuring this out, but how exactly am I supposed to dose magnesium again? It's been a long time since I've had to worry about this, but after a year of my tank just managing fine on water changes alone, my mag levels are trending downward and I think I need to start dosing.

There seems to be so many ways to do it, epsom salts, epsom salts plus some other magnesium chemical, dosing with a doser, dosing mixed in with the calcium solution, dosing by hand once every so often, etc. etc. etc.

What does everyone here do to maintain magnesium levels and why?

lastlight · #2 05-16-2013, 07:21 AM

i've got the brs chemicals on hand for the day i need to dose but so far so good.even on my 400 full of sps i never had to dose it and i had stockpiled a lot lol.

asylumdown · #3 05-16-2013, 07:33 AM

Yah I'm not sure what's causing this! My usual sources of salt ran out of H2Ocean briefly so I used a box of reefers best and that's when I first noticed a precipitous decline, but even after 3 water changes in a row using my trusty old barrel of H2Ocean again I'll be d*mned if I can keep my levels above 1240 week over week anymore. They used to hover just under 1400 without me dosing a single thing.

I just bought a boat load of stuff from BRS on the group buy. I can't believe I didn't by mag supplements.

Brett, which BRS stuff do you have? Is it the two part Mag chloride and sulfate mix?

daplatapus · #4 05-16-2013, 01:16 PM

I use the BRS Mag Sulfate and Mag chloride. I mix as per instructions and dose via their 1.1ml/minute doser every day. Seems to work great for me. It's been about a year.
I do it this way because simply because of the ease. A 1 gal jug lasts me over 6 months easy. I have it by my calcium reactor and just eye it whenever I'm down there to make sure the line feeding back into the sump isn't clogged or the jug hasn't run dry.

Myka · #5 05-17-2013, 12:01 AM

I use Fauna Marin Magnesium chloride. I add 2 cups to my 15-gallon waterchange tub along with 1 tbsp epsom salt (Magnesium sulfate) using H2Ocean salt. The "perfect" ratio according to Randy Holmes-Farley (I think it was him) is 8.5:1. You do not want to use epsom salt as the primary source because there will be too much sulfate in the tank. It takes a lot of powdered magnesium product to raise magnesium, meaning there is a lot of chloride (or sulfate) being added. Adding the product this way, I do not have to dose magnesium otherwise.

lastlight · #6 05-17-2013, 01:46 AM

Yeah I use the mag chloride and sulfate mix. Or will someday lol. There was a time when I did have to occasionally dose it.

reefermadness · #7 05-17-2013, 01:57 AM

My guess is the new salt mix is lower in magnesium. Personally I would be happy with 1240ppm and leave it be. If it lowers to 1200ppm you might want to add 100ppm and you can safely do that with epsom salt USP from any pharmacy. Use the reef chemistry calculator to figure out how much, add it to some RO/DI and split the dose into two days.

Myka · #8 05-17-2013, 02:20 AM

I missed answering the "and why?" part of your question... The way I do it is easy, it works, and I don't forget it.

I add potassium in the same manner.

Delphinus · #9 05-17-2013, 04:19 AM

As Myka stated it takes a lot of Magnesium to raise a Mg reading in a tank, so don't be shocked.

I just top up my SW, I know how to much to add to make my ingoing water 1500Mg and that seems to combat the Mg drain just fine. I was using Mag sulfate and Mag chloride from Eli and use the same dosing instructions as per BRS..

michika · #10 05-17-2013, 02:38 PM

Quote:

Originally Posted by daplatapus

I use the BRS Mag Sulfate and Mag chloride. I mix as per instructions and dose via their 1.1ml/minute doser every day. Seems to work great for me. It's been about a year.
I do it this way because simply because of the ease. A 1 gal jug lasts me over 6 months easy. I have it by my calcium reactor and just eye it whenever I'm down there to make sure the line feeding back into the sump isn't clogged or the jug hasn't run dry.

I too tose BRS Magnesium sulfate and Magnesium chloride and then dose my system via doser (peristaltic) pump. My system is larger then most's so I dose a lot more then most do. I struggle to keep my MG up because I have clams and they do have a noticible uptake. I aim for ~1350ppm-1400ppm personally. As a result I dose in a continuous fashion; nightly.

Things to note; dose your Mg at a different time then your Ca or dKH additives. Add into a high flow area and do it SLOWLY. A Magnesium swing too high might take your system a LONG time to work through, barring water changes.

I dose my Mg at night and keep a buffer of around 4 hours before or after my Ca or dKH was dosed.