Mg in the tank

[reedman]

I was hoping to start a discussion of Mg in the tank; It's importance, what level is appropiate, how to maintain it, and the affects of not maintaining it.

I've always seen levels quoted at about 1250-1350.

For maintenance I have seen people using Epsom salts and also Mg chips in the Ca Reactor. The epsom salts I have seen some controversy on in recent times and wonder what the side affects are and at what level of dosing they start to manifest.

Anybody have some good info/personal experience?

 

[reedman]

Here's one link to start off

http://www.advancedaquarist.com/issues/oct2003/chem.htm

Korallen-zucht sells a pure magnesium granulate (designed for ZeoVit system, but could be used anywhere). People are putting this in their Ca reactors to supplement the Mg levels.

 

[jlehigh]

Good topic Reed. Thinking waayyyyy back to one of my first PSAS meetings we had Warner marine provide a session on water chemistry 101. I recall MG directly impacting the balance of CA and ALK. I also recall elevated CA levels (500&up) resulting in a decrease in MG which resulted in a very difficult imbalance to correct.

Okay enought talking outta my arse. I'll see what other write-ups I can dig up.

 

[shallowreef]

i will be looking forward to the posts in this thread

 

[Scooterman]

I've had issues with low MG & because of that I could never keep ca, alk in balance or even raise the ca to a desired level until MG was raised in balance.

 

[NaH2O]

Here is a quote from the article linked above by Reed:

Magnesium is an important ion for reef aquarists. In addition to its many biological functions, it serves to prevent the excessive precipitation of calcium carbonate from both seawater and aquarium water. Since both calcium and alkalinity are very important to organisms that we keep, making sure that they are not lost to excessive precipitation is an important part of aquarium husbandry.

With regards to what levels we should keep our Magnesium at, Randy Holmes-Farley recommends 1250-1350 ppm, and he notes NSW levels 1280 ppm. The following quotes are taken from the article: Reef Aquarium Water Parameters by Randy Holmes-Farley

Magnesium's primary importance is its interaction with the calcium and alkalinity balance in reef aquaria. Seawater and reef aquarium water are always supersaturated with calcium carbonate. That is, the solution's calcium and carbonate levels exceed the amount that the water can hold at equilibrium. How can that be? Magnesium is a big part of the answer. Whenever calcium carbonate begins to precipitate, magnesium binds to the growing surface of the calcium carbonate crystals. The magnesium effectively clogs the crystals' surface so that they no longer look like calcium carbonate, making them unable to attract more calcium and carbonate, so the precipitation stops. Without the magnesium, the abiotic (nonbiological) precipitation of calcium carbonate would likely increase enough to prohibit the maintenance of calcium and alkalinity at natural levels.

An aquarium's corals and coralline algae can deplete magnesium by incorporating it into their growing calcium carbonate skeletons. Many methods of supplementing calcium and alkalinity may not deliver enough magnesium to maintain it at a normal level. Settled limewater (kalkwasser), in particular, is quite deficient in magnesium. Consequently, magnesium should be measured occasionally, particularly if the aquarium's calcium and alkalinity levels seem difficult to maintain. Aquaria with excessive abiotic precipitation of calcium carbonate on objects such as heaters and pumps might suffer from low magnesium levels (along with high pH, calcium, and alkalinity).

So what do you think about this last quote? Also, in the other article Reed linked you can see Coralline algae uses a higher percentage of magnesium. Do you think if you have a coralline algae explosion in your tank, you should be checking and supplementing for Magnesium? Or will water changes be able to handle the depletion? What about when using a kalk reactor....are your magnesium levels going to be difficult to maintain?


There was some good debate between Mojo and Boomer on the topic of Magnesium. The start was in this thread: Magnesium....and the finish was this thread: MOJO!!! So much for my Mg comment

An article from the first thread - Magnesium: Calcium's little sister

In short, while magnesium carbonate is not supersaturated in seawater (or in reef tanks), and will not precipitate on its own, magnesium is attracted to calcium carbonate surfaces where the carbonate ions are already held in place by the calcium ions. With the carbonate ions held in place, magnesium finds this an attractive place to precipitate. A similar effect happens for phosphate and many organics, where they precipitate onto the calcium ions that are held in place by the carbonate ions — but that's another story for another day.

I also found this PDF file interesting...it was posted by Mojo in the second thread I linked above: Distribution of Magnesium in Coral Skeleton

 

[-=dieseldave=-]

Sulfate is the issue with Epsom salts although I not sure of any real data on how it affects our tanks and at what level it starts to become to be toxic, if ever. I believe that in seawater the ratio of Mg to Sulfate is close to 2/1. But in Epsom salts the sulfate out weights the mg in the mix.

I use magnesium chloride when looking to raise my mg levels.

I maintain my calcium though weekly water changes, I add magnesium chloride to the newly mixed water for the water change. I try to get the mg to 1350 in the new water. I Test every new bucket of salt I use for MG and Alk and Ca then I know how much I need to add to the newly mixed water.
I have looked at the Zeo Mg for my reactor and have not yet tried it. My only thought is that it would only maintain the mg after the lengthy process of getting the right ratio of Zoe mg to ARM.

As for the effects of low (1000ppm-) or High (1500ppm+) I imagine the effects would be different for different life forms in our tanks. But there would be effects for sure.

 

[MikeS]

I too am a firm believer that Ca, Mg and Alk should all be kept in proper ratios to NSW values dependant on the particular salinity of your individual system.

I have also found that it is much easier to prevent imbalances by adjusting my salt mix for Mg, Ca and Alk (dependant on salinity) to the proper NSW ratios prior to adding it to the tank. If your tank is in balance, doing this insures that the new water going in is properly balanced, making it less likely that an imbalance will occur providing your Ca, Mg and Alk suppliments going into the tank are being done properly.

MikeS

 

[mojoreef]

Yea Mag is an important player for sure and dont let it get to low as it is a bear to get back to proper levels. Its one of those elements that binds with most things so much of what you dose to get to proper levels goes out of solution right away. I let mine get down to the 900's once and man did I have to add a ton of it to get it back again.
Epson salts work but as mentioned above your also adding sulfate, so it is best to make epson salt only about 25% of what you dose to get it back again. I used Warner Marines Magnesium chloride to facilate the balance.


MIke

 

[reedman]

Great info folks. Thx!

 

[CarlaW]

I have always heard that the ratio of Mg to Ca should be 3 to 1. Is this a solid fact????

 

[steve-s]

It is but as Mike pointed out above, the numbers achived should be in balance with the salinity for best results. Exact numbers not really being needed though.

Cheers
Steve

 

[MikeS]

heres a link that discusses Mg depletion when using kalk...

http://www.advancedaquarist.com/issues/dec2003/chem.htm

MikeS