Something I have been battling for a long time to understand, are the relationship between some supplements and balances between certain minerals we find in our seawater.
1.) Why do we need them in our aquaria?
2.) What type of Coral/Fish/Critters need it to grow?
3.) Substitutes for the DIY Enthusiast.
4.) How much of each we need in our aquaria to maintain a balanced system.
So, I did what most of us do, and started reading up on everything I could find wrt Magnesium, Calcium, Iodine and Strontium as well as the balance between them.
I will give credit at the bottom of the page to all the authors of these various articles.
This is my summary as to the above chemicals/additives and basically a guide to all the newbies or interested parties:
Magnesium in Our reef Systems
Magnesium:
Magnesium is the third most abundant ion in seawater, behind sodium and chloride. In seawater magnesium is present at approximately 1285 ppm, hence most test kits refer to the right DKH for Magnesium to be between 1250 and 1350ppm.
Magnesium's primary importance in reef aquaria is its interaction with the calcium and alkalinity balance.
The primary benefit of Mg is that it allow calcium and bicarbonate levels in the water to exist at supersaturated levels. In laymen's terms, having high Mg allows you to maintain higher Ca/Alk.
Maintaining Mg levels is necessary to hold Ca and Alk levels where you want them.
Why do I say that??
Answer: Whenever calcium carbonate begins to precipitate, magnesium binds to the calcium carbonate crystals' growing surface. 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, precipitation of calcium carbonate would most probably increase enough to prevent the maintenance of calcium and alkalinity at natural levels.
Fortunately , The primary source of magnesium in our aquariums is the artificial or natural seawater we use to run/start our systems and with which any water changes are performed. Another source of magnesium is fish food. Magnesium is present in many such foods at fairly high concentrations, but not enough to have a huge impact on magnesium levels.
Other needs for Magnesium:
Normal calcium balance in organs
Healthy muscles
Healthy nerve transduction
Healthy calcium balance in blood vessel
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In addition to the magnesium used in the process of calcification, many (if not all) organisms take it up directly from seawater. Organisms ranging from bacteria8-10 to fish11 take up magnesium, but the amount is generally much smaller than that used during calcification. In many cases, there is so much magnesium in seawater that the organisms expend more effort pumping excess magnesium back out than they do trying to take it up.
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Ref: Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com
So you want to know the meaning of the big word:
calcification???
Calcification:
Hermatypic coral species are those which form reefs containing the unicellular algae called zooxanthellawhich can have densities of up to 1 million cells per cm2.
These algae need to have light to be able to carry out the process of photosynthesis, using the carbonic gas dissolved in the sea water, nitrogen and mineral phosphorus to produce the organic matter required by the polyps.
By causing a shift in the carbonate balance, they promote the precipitation of the calcium carbonate on which the coral skeleton is based, and thus induce the process of CALCIFICATION.
I have always been adding Magnesium and kept them at the highish DKH range, mainly to boost the growth of coralline algae as it has high magnesium content.
On the table illustrated below, we can see how much Magnesium content we can find in Corals etc
Table 1. Magnesium in Calcium Carbonate Skeletons Organisms Magnesium content of skeleton (weight %) Reference Corals: Suborder Asterocoeniina and Faviina 0.07 - 0.36%
Suborder Fungina 0.095 - 1.22%
Fungia actiniformis var.
palawensis 0.091%
Suborder Caryophylliina 0.18 - 0.21%
Suborder Milleporina 0.12 - 0.53%
Millepora sp. 0.12 - 0.53%
Suborder Stolonifera 2.98 - 3.52%
Family Tubiporidae 2.98 - 3.52%
Tubipora rubrum 2.98 - 3.52%
Family Dendrophylliidae 0.05%
Family Porites 0.095 - 1.22%
Porites lobata 0.40 - 1.22%
Family Pocillopora 0.34%
Family Dendrophyllia 0.05%
Gorgonia: Eunicella papillosa,
E. alba,
E. tricoronata, and
Lophogorgia flamea 2.2 - 2.7%
Other Organisms: Coralline algae in general >1%
Coralline algae:
Lithophyllum and
Lithotamnium 2.0 - 2.8%
Calcareous alga:
Corallina pilulifera 4.4%
Benthic marine Ostracoda (crustaceans) 0.5 - 1.3%
Coralline algae that normally packs a large amount of magnesium into their calcium carbonate deposits has been shown to incorporate less magnesium when the magnesium content of the water is reduced.
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How does magnesium impact the balance of calcium and alkalinity in reef aquaria?
In order to answer that question, one has to have a basic understanding of the calcium and carbonate systems in seawater. These systems have been discussed in detail in a variety of previous articles, so I won't go into them here in great detail. In short, calcium carbonate (CaCO3) is supersaturated in seawater,meaning that given enough time calcium ions will interact with carbonate ions and precipitate as calcium carbonate. If you push the concentration of either too high, CaCO3 will start to precipitate. Magnesium interferes with this process, permitting both calcium and carbonate to be elevated above where they would be in the absence of magnesium.
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Ref: Stephen Spotte's book _
Captive Seawater Fishes
And now for the substitute in the Commercially bought Magnesium Supplement:
03 Basic Supplement Solutions:
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1. Using Epsom salts only, dissolve 8 cups Epsom salts in 3.8lt of water, and use that to supplement magnesium in amounts determined by using this calculator link shown below. This recipe is the least preferred of the three, but can be acceptable if used for small amounts of supplementation, or if combined with at least 30% water changes per month. It is also a more reasonable choice if calcium chloride and sodium bicarbonate (baking soda) are used in large amounts to supplement calcium and alkalinity.
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2. Using MAG flake only, dissolve 8 cups magnesium chloride hexahydrate in one gallon of water, and use that to supplement magnesium in amounts determined using this calculator below, with the entry "Randy's Recipes 1 and 2 Versions A and B," and ignore for this purpose what those designations mean. This recipe is adequate, but not quite as balanced as #3 below. This choice is not a good way to go if calcium is supplemented by calcium chloride, because together they will force chloride excessively high.
3. Using both Epsom salts and MAG flake, dissolve 7¼ cups MAG flake and ¾ cup Epsom salts in one gallon of water, and use that to supplement magnesium in amounts determined using this calculator below, with the entry "Randy's Recipes 1 and 2 Versions A and B," and ignore for this purpose what those designations mean. This recipe is preferred, but its advantage over recipe #2 is minimal in most cases.
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Ref: Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com
Here you can find an online Calculator to help you with the above 03 methods:
Reef Chemistry Calculator
What if I dose too much:
In very high overdose cases, the 1st you will notice, is snails that might be dying, especially stomatella snails
References and Credits:
· A Homemade Magnesium Supplement by Craig Bingman Aquartium Frontiers, June 1999.
http://www.animalnetwork.com/fish2/a...io/default.asp
· Magnesium -- Part I by Craig Bingman, Aquarium Frontiers, March 1999.
http://www.animalnetwork.com/fish2/a...io/default.asp
· Magnesium -- Part II by Craig Bingman Aquarium Frontiers April 1999.
http://www.animalnetwork.com/fish2/a...io/default.asp
· Calcium and Alkalinity by Randy Holmes-Farley, Reefkeeping, April 2002
Calcium and Alkalinity by Randy Holmes-Farley - Reefkeeping.com
Do-It-Yourself Magnesium Supplements for the Reef Aquarium by Randy Holmes-Farley - Reefkeeping.com
And that basically brings me to the end of this Supplement, next I would like to address PH, Alkalinity and Calcium as well as the General hardness (GH or dGH), but I am not done with it as yet.
Here is a quick table to ponder on:
PH
