Dosing Mg

[Reef Pilot]

My Mg used to always be up in the 1400 range, but has been dropping, and getting a little low now, in the 1200 range. I have never dosed Mg, but may have to start.

However, I don't have a 3rd dosing pump. Does manual dosing work with MG or is that too erratic with adverse effects on the corals? Or could I add some Mg mix to my Ca dosing container and do both at the same time?

I have had a bit of an algae problem after I combined my tanks into one sump, and my P04 was up a bit for a while. And I vaguely recall reading somewhere that low Mg can also contribute to algae. Is that true?

[tang daddy]

You can safely raise 100ppm of mg daily, for your size system it could mean lots. I had to raise mine over 400 ppm and it took me 2 weeks and tons of mg.

You could build a make shift drip system out of an old milk jug or anything that holds water, then calculate how much mg is needed to your total water in your system, and using gravity syphon with a irrigation nossel drip it in over a week.

Eg. 2 cups of mg to 1g of ro, drip it at 1 drop per second. Test it after you have finished adding the mg and see where it's at then you can mix up another batch.

Surprisingly most people don't have to dose it, I am dosing 180 ml for my 90g of water volume daily. That's alot considering of small water volume... I couldn't keep up and had to get a doser.

[Reef Pilot]

Surprisingly most people don't have to dose it, I am dosing 180 ml for my 90g of water volume daily. That's alot considering of small water volume... I couldn't keep up and had to get a doser.

Yeah, that's a lot, alright. I have never had to dose Mg so far, and hopefully won't have to do that much. That's why I would like to start off with manual dosing. And even try combining it with my Ca dosing, if that works. I really don't want to get another doser...

[Bblinks]

Even with my calcium reactor filled with 20% magnesium I still find myself having to add it manually. Like T-diddy said, 100 ppm per day is the maximum. I have dosed up to 2.5 gallons at a time without any problems and that only raised my mag from 1250 to 1320.

[tang daddy]

Even with my calcium reactor filled with 20% magnesium I still find myself having to add it manually. Like T-diddy said, 100 ppm per day is the maximum. I have dosed up to 2.5 gallons at a time without any problems and that only raised my mag from 1250 to 1320.

T-diddy dat new.... I like T-Dot! :lol:

[Reef Pilot]

My Mg has been running about 1260 ppm lately (used to be around 1400), so decided to start raising it with manual dosing. Yesterday I added 125 grams of Seachem Reef Advantage Magnesium to a 230 gal water vol. This is only 1/2 the maximum dose they recommend for one day. And to raise it all the way to 1350, their dosing calculator says I need to add about 8 or 900 grams, which seems like a lot to me.

So today, I test my Mg again to see what effect it had. And to my surprise, my Mg is now higher than 1500, which is the max I could test for with my Salifert test kit!! WTF!!! It should only have gone up by maybe 10 - 15 ppm according to their instructions.

I reread and reread the instructions, and did more research on the web, but can't figure out what I did wrong.

I also tested my alk (8 dKH) and Ca (400 ppm) and it did not change much from yesterday. And everything in my tank(s) look normal.

I will test again tomorrow. But any ideas what is going on here??

[e46er]

Strange maybe your initial test was off?
I have used lots of seachem products (mainly my old planted tank) but a few for SW and Their magnesium is the single only product I haven't liked.
My mg was low and over like 2 weeks I had dumped the entire 600 g tub in with no increase.
I got some mag. From little silver max and his product rasied it exactly what he said it would with an online calculator.

My guess is your original testing was off

[Reef Pilot]

Tested again today, and it came in at 1290 which makes more sense. My guess is that yesterday I may not have pulled in the test solution to the top mark in the syringe. I have tested Mg many times before, and never had a bad test, so a little strange that it would happen right after adding Mg.

Anyway, will add more MG today, and keep tracking it.

[Proteus]

I had the same issue with seachem mag and there calculator. I ended up cutting the recommended dose in half and making sure the tanks water mixed for 2 hours before retest

[Reef Pilot]

Yeah, it definitely doesn't mix easily. Just added another 125 grams this morning, and will test again tomorrow to see if it brings up my Mg. I bought the 600 gram size, so I might as well use it up.

[tang daddy]

You should usually test 6 hrs after dosing... Ideally 12 hrs as it will stabilize.

I dosed alk before and tested 1 hr after a larger dose. It skewed the test as it was sitting at 10dkh from 7 originally, tested 24 hrs later and it was at 7.5....

Conclusion, It is best to test the next day after dosing.

[Madreefer]

A cheap easy alternative is
50lb bag of Easy Start brand icemelter for your driveway $40
4kg jug of Epsom Salts $5
Mix it 11-1
I use 1/2cup per 5gallons of freshwater in my top up resevoir.
Been using this for a couple of years now. You can't really argue that it's unsafe for reef tanks as I learned this from whatcaneydo and well, look at pics of his tank:biggrin:

[Reef Pilot]

Well, I used up my 600 g Mg from Seachem, and managed to raise it from 1260 to 1350. Didn't seem to make any difference to my alk or Ca consumption and parameters, and my corals were not at all affected.

So will leave it for now, and see where it goes from her.

[Reef Pilot]

A cheap easy alternative is
50lb bag of Easy Start brand icemelter for your driveway $40
4kg jug of Epsom Salts $5
Mix it 11-1
I use 1/2cup per 5gallons of freshwater in my top up resevoir.
Been using this for a couple of years now. You can't really argue that it's unsafe for reef tanks as I learned this from whatcaneydo and well, look at pics of his tank:biggrin:
Well, my Mg didn't stay up for very long, back down to 1260 now. So I think I am going to have to get serious about dosing.

Where do you buy this Easy Start ice melter? And where is a good place to get a 4 kg jug of Epsom salts?

I don't use a top off reservoir. After mixing the Easy Start and Epsom Salts (11:1), can I add that mixture (after figuring out the appropriate amount) to my Ca dosing? Or do I need to set up a 3rd dosing pump? And what time of day is it best to dose Mg? Currently I dose Ca during the day and Alk at night.

[Madreefer]

I picked up mine from Amco. The epsom salts from Shoppers Drug Mart. I add a half a cup of the mixture to 5G of freshwater for my reservoir. Stays consistant at 1350. Whatcaneyedo is the dude that got me on to this. I'm pretty sure he adds a cup of the mixture to his water change but dont quote me on that. Shoot him a PM he's pretty helpful. Good luck bro

[Reef Pilot]

I picked up mine from Amco. The epsom salts from Shoppers Drug Mart. I add a half a cup of the mixture to 5G of freshwater for my reservoir. Stays consistant at 1350. Whatcaneyedo is the dude that got me on to this. I'm pretty sure he adds a cup of the mixture to his water change but dont quote me on that. Shoot him a PM he's pretty helpful. Good luck bro
Thanks. Don't think we have an Amco wholesale in the lower mainland. Anybody know where I can get the Easy Start here?

[Aquattro]

Every time I read these threads, I'm almost tempted to measure my Mg :)

[Reef Pilot]

Every time I read these threads, I'm almost tempted to measure my Mg :)
Are you suggesting I should hold off? I sure would like to.

What gets me is my Mg was running at 1260 before I raised it to 1350, and then a month+ later it is back to 1260??

And I should add that my Ca and Alk have been stable all along with my dosing. Maybe I should leave the Mg alone?

[Aquattro]

Are you suggesting I should hold off? I sure would like to.



No, suggesting I should get off my lazy ass and test my Mg :)

[Madreefer]

I've overdosed my Mg before and played around with it alot trying to combat bryopsis. I've also brought it up by way over 100ppm in a day. It's really not a big deal as if you were dosing Ca. Worrying just makes you lose sleep. Unrelated to you but on side note, I might add that this wont work on bryopsis thats just the Kent stuff.

[Aquattro]

Ok, I was inspired. Mg is ~1170pm. lol Almost perfect!!

[lastlight]

I'm amazed you can balance the other two with mg so low. Maybe your kit sucks or it's diff for reactor folks?

I don't have to dose mg so long as I adjust my water changes to 1400. H2ocean is low. I add 160mL to 10g of new water.

Instead of dosing you could prob raise your water changes up some. What does your mix measure in at?

[gregzz4]

can I add that mixture (after figuring out the appropriate amount) to my Ca dosing? And what time of day is it best to dose Mg? Currently I dose Ca during the day and Alk at night.
Not a good idea to mix the Mg and Ca. The Mg will cause Ca sulphates to precipitate and ruin your Ca mix so you'll need a third doser. But many get by with hand dosing as it's not so much once balanced
You can dose the Mg anytime between your other dosing. Just pick a time dead center between your Ca and Alk timers - day or night is fine as far as I know
And if you're not needing to add much (once balanced), you could get by with a cheap daily drip setup, or just dump it in
I don't even know anyone with a dedicated Mg doser ... but I'm sure there's lots out there
I know if I had to dose it I'd have another pump :rolleyes:

[Doug]

Ok, I was inspired. Mg is ~1170pm. lol Almost perfect!!



Ok so the rest of us following normal reefing parameters, like measuring ph, keeping magnesium at suggested proper level of 1350ppm, using something other than crappy old crushed coral in a reactor and our tanks are not half as nice as yours.......LOL....:lol:

Oh ya and chucking led,s. :lol:


Do you add a magnesium additive to the crushed coral or that level is what it maintains.

[Aquattro]

Ok so the rest of us following normal reefing parameters, like measuring ph, keeping magnesium at suggested proper level of 1350ppm, using something other than crappy old crushed coral in a reactor and our tanks are not half as nice as yours.......LOL....:lol:

Oh ya and chucking led,s. :lol:


Do you add a magnesium additive to the crushed coral or that level is what it maintains.

Ya, it's a low maintenance tank :) Nope, no additives, that's just where it sits. That's about where it was last year when I measured it.
To be honest, pre 2008, nobody even cared about Mg. Never saw it for sale or saw test kits. It's a recent requirement for tanks. I guess I have older corals, they don't care either -lol

[Doug]

Ya, it's a low maintenance tank :) Nope, no additives, that's just where it sits. That's about where it was last year when I measured it.
To be honest, pre 2008, nobody even cared about Mg. Never saw it for sale or saw test kits. It's a recent requirement for tanks. I guess I have older corals, they don't care either -lol

Ya I guess thats it. Im old and dont care about my magnesium either..:lol:

[Reef Pilot]

Not a good idea to mix the Mg and Ca. The Mg will cause Ca sulphates to precipitate and ruin your Ca mix so you'll need a third doser. But many get by with hand dosing as it's not so much once balanced
You can dose the Mg anytime between your other dosing. Just pick a time dead center between your Ca and Alk timers - day or night is fine as far as I know
And if you're not needing to add much (once balanced), you could get by with a cheap daily drip setup, or just dump it in
I don't even know anyone with a dedicated Mg doser ... but I'm sure there's lots out there
I know if I had to dose it I'd have another pump :rolleyes:
Well, I did just buy a 3rd doser (50ml/min high speed type), so I could do that. But that brings me back to the question of what type of Mg to buy. I could not find that East Start stuff around here. And not sure if I can trust some of the ice melters that I saw online, as they don't list ingredients.

I guess I could just buy more of that Seachem Advantage Mg from J&L, but it is not cheap for the amount I would require on an ongoing basis.

[Doug]

Well, I did just buy a 3rd doser (50ml/min high speed type), so I could do that. But that brings me back to the question of what type of Mg to buy. I could not find that East Start stuff around here. And not sure if I can trust some of the ice melters that I saw online, as they don't list ingredients.

I guess I could just buy more of that Seachem Advantage Mg from J&L, but it is not cheap for the amount I would require on an ongoing basis.


Thats what I used before. I now have bulk dosing from BRS. I find I dont have to add much magnesium to keep it close to 1400ppm.

[Reef Pilot]

Thats what I used before.
Which one, Easy Start or Seachem?

[Doug]

Seachem. I used their two part for years and always liked it. Yes agreed with you though, at more expense. I like the BRS products. The magnesium comes as a 2 part to mix in the container. Magnesium sulphate and Magnesium Chloride

[Doug]

Once my co2 reactor is running I will stay with this magnesium additive for the occasional top off.

[Madreefer]

http://www.homehardware.ca/en/rec/index.htm/Outdoor-Living/Yard-Maintenance/Snow-Removal-Aids/Ice-Snow-Melting/Ice-Melt/20kg-Calcium-Chloride/_/N-2pqfZ67l/Ne-67n/Ntk-All_EN/R-I5548231?Ntt=Ice+Melt

I'm sure theres a Home Hardware in your area. Give this a look

[Reef Pilot]

Yes, we do have a Home Hardware in Langley. I notice from the ingredients that it is 83 - 87% MgCl. But what is the rest? I am a little leery of being the guinea pig on a product used in my reef tank. I noticed the same at Rona, Canadian Tire and Home Depot. They have some MgCl products, but none of them very pure.

Edit: Just noticed that the Home Hardware product is Calcium Chloride, not MgCL.

[Rogue951]

If you're doubting chemical purity just go order from BRS or I believe one of the sponsors has bulk chemicals as well (if you can't make it to the border). I use BRS stuff and it always mixes crystal clear.
Hell if you really need MG I can spare enough to mix 2 or 3 gallons of MG solution till you order.
I go through CA and ALK 4x faster than my mg so I always have extra when i order their bulk mix kits.


You already bought another doser, but you could have done the knot in the airline trick for a slow addition.

[Reef Pilot]

Thanks for the offer. At the moment, still researching the subject. I could buy from BRS (I live only 20 min from the border), although the loonie is down pretty low these days. But would like to buy locally if I can.

I just bought the extra doser from a canreefer, and wanted it also as a backup to my other two that I use now. So I could put it to use with Mg. But yes, the air line with a knot would probably work almost as well.

[gregzz4]

But yes, the air line with a knot would probably work almost as well.
Or a micro ball valve (http://www.jlaquatics.com/phpstore/store_pages/product-info.php?product_ID=tf-plmvbb)
These are great for drip acclimation too, amongst other stuff