Magnesium
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mojoreef said:
If you add Magnesium Carbonate buffers then yes Alk will increase. However, magnesium getting out of balance over time will not affect measured alk.
Magnesium and Alk measured in an equilibrated tank are independant...unless you have problems with precipitating Lime. In this case Magnesium carbonate would co-precipitate with calcium carbonate and could lead to a reduction in Alk. However, this indicates a problem other than Mg levels (unless they are very low). As long as everything is staying in solution, the Mg and CO3/HCO3 will exist as stabilized but independant ions and the alk will be available for buffering via acid-base reactions.
If you start to see lime precipitating, then it will contribute to the loss of Alk. Otherwise, no it should not according to my thinking.
Sincerely...Collin
Boomer
Well-known member
Mike
There have been a number of low alk Mojo
Well that would be a direct result of the mag and cal levels no??
Ok I think we are on different paths here, you lost me, lol
Ok I'll give you a compass to find your way back
It sounds like you are saying oceanic has high Mg and Ca, thus the reason for low Ak. My answer is no, all a salt manufacture has to do is add more MgCl and CaCl to the mix, with little buffer ( as in baking soda), if they added more buffer the Alk would get higher. They would not want to add to much buffer or the Ca and Mg would just precip out of solution.
Your reading assignment
Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm
I know of no safe way to remove Mg, I would leave it alone as Collin has suggested or do WC. Mg can have a toxic effects but only when it gets much, much higher.
There have been a number of low alk Mojo
Well that would be a direct result of the mag and cal levels no??
Ok I think we are on different paths here, you lost me, lol
Ok I'll give you a compass to find your way back
It sounds like you are saying oceanic has high Mg and Ca, thus the reason for low Ak. My answer is no, all a salt manufacture has to do is add more MgCl and CaCl to the mix, with little buffer ( as in baking soda), if they added more buffer the Alk would get higher. They would not want to add to much buffer or the Ca and Mg would just precip out of solution.
Your reading assignment
Magnesium in Reef Aquaria
http://www.advancedaquarist.com/issues/oct2003/chem.htm
I know of no safe way to remove Mg, I would leave it alone as Collin has suggested or do WC. Mg can have a toxic effects but only when it gets much, much higher.
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Ok I will bite, lol Chemistry is my friend...chemistry is my friend
here is my limited understanding. Magnesium limits the formation of calcium carbonate crystals, to the point at which this formation can even stop, if that is the case then calcium carbonate is not forming, which is a problem for corals as they need the carbonate to pull the calium out of thier cell structure. Now also with the carbonate level being low to start with even at natural mag levels calcium carbonate percipatation will be significantly.
So with calcium ions binding to the carbonate and magnesium ions binding to the carbonate ion how is it supposed to do it job as a buffer or in percipatation? Also doesnt mag poison the seed surface so calcium carbonate wont precipatate?? doesnt that pose a large problem for a corals calcification process??
Ok I am tied to the whipping post boys...have at me :badgrin:
Mike
here is my limited understanding. Magnesium limits the formation of calcium carbonate crystals, to the point at which this formation can even stop, if that is the case then calcium carbonate is not forming, which is a problem for corals as they need the carbonate to pull the calium out of thier cell structure. Now also with the carbonate level being low to start with even at natural mag levels calcium carbonate percipatation will be significantly.
So with calcium ions binding to the carbonate and magnesium ions binding to the carbonate ion how is it supposed to do it job as a buffer or in percipatation? Also doesnt mag poison the seed surface so calcium carbonate wont precipatate?? doesnt that pose a large problem for a corals calcification process??
Ok I am tied to the whipping post boys...have at me :badgrin:
Mike
Boomer
Well-known member
I just sharpened my whip
Magnesium limits the formation of calcium carbonate crystals, to the point at which this formation can even stop......if that is the case then calcium carbonate is not forming, which is a problem for corals
This has nothing to do with corals. You are comparing apples and oranges. It is what happens on bare fresh surfaces of carbonate minerals ( gravels), which means high magnesium carbonates are not being formed on the surfaces of fresh carbonate minerals, which means the Mg, Ca and Alk are staying in solution, making it available for corals. Dolomitic gravels will have the highest effect of high Mg calcite precip out on the surface of the dolomite mineral. Pure Calcite will be the least. However, pure dolomite is less soluble than pure calcite. This is may/can be a temporary thing. These surface poisons are very soluble and can/may go back into solution easy. Precip can also happen on heater, glass etc, which is a little different chemistry. Coral biology and their formation of Calcium carbonate is another beast You are comparing what happens to a bare rock surface to what happens inside a live coral, not the same thing. In a reef tank or even in the ocean this doesn't' happen much, as the gravels get a bacterial surface coating and precip will be nil, if at all. In a new tank it would/may be a temporary thing.
You did not read your homework assignment now did you
How does magnesium interfere with precipitation of CaCO3? The primary way involves magnesium poisoning the surface of growing CaCO3 crystals, slowing the precipitation. It can, in fact, be slowed to the point where it simply does not happen at rates problematic to an aquarist. In the following discussion it is important to remember that, other things being equal, alkalinity is a good indicator of the concentration of carbonate. So higher alkalinity equates to higher carbonate.
In short, while magnesium carbonate is not supersaturated in seawater (or in typical reef aquaria), 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 bind.
After a short time in seawater, a virgin calcium carbonate surface quickly attains a thin coating of Mg/CaCO3 (magnesian calcite) as magnesium pushes its way into and onto the crystal surface. Eventually, the surface contains a substantial amount of magnesium. The extent to which this happens depends on the underlying mineral, and is apparently much more extensive on calcite than aragonite. It also depends upon the relative amounts of calcium and magnesium in the water. Regardless, a new type of material is formed that contains both calcium and magnesium.
This new mineral surface containing both calcium and magnesium is not a good nucleating site for precipitation of additional calcium carbonate (as aragonite or calcite), and precipitation of additional CaCO3 slows down substantially.
In Captive Seawater Fishes there is an extensive discussion of the impact of magnesium on the calcium/carbonate system, including a set of data that indicates the magnitude of the impact that magnesium can have.25 In this experiment, batches of artificial seawater were made up with varying magnesium and carbonate levels. The scientists then measured how long it took for calcium carbonate to precipitate from each solution. Not surprisingly, the higher the carbonate was raised, the more rapid was the precipitation of calcium carbonate.
More interestingly, the magnesium levels were found to have a very large impact on the rate of precipitation. In batches with no magnesium, and at natural calcium and elevated carbonate levels, calcium carbonate was found to precipitate in minutes. With a natural seawater level of magnesium added to that mix, the precipitation was delayed to 13 to 20 hours. With double the natural magnesium concentration, the precipitation was delayed to 22 to 29 hours.
Even more strikingly, at a lower level of carbonate (closer to that of natural seawater and probably similar to that in many reef aquaria), precipitation was delayed from a few minutes in the absence of magnesium to 750 hours in the presence of natural levels of magnesium. Consequently, magnesium has a big impact on the rate of precipitation of calcium carbonate (a fact that has been confirmed by many researchers).
But what does that have to do with a reef aquarium? One situation in which calcium carbonate can precipitate involves adding calcium carbonate seed crystals of some type to the aquarium. For example, by adding calcium carbonate sand or one of the calcium carbonate supplements like Aragamight or Kent’s Liquid Reactor.26
A second situation where solid CaCO3 forms is when abiotic precipitation initiates in the aquarium.24 This precipitation happens when supersaturation is pushed to unusually high levels (either in the tank as a whole, or in localized regions). This rise in supersaturation can be caused by a rise in pH (which increases the amount of carbonate present by converting bicarbonate into carbonate), a rise in temperature (as on a heater or pump impeller; the temperature rise decreases the solubility of calcium carbonate and also converts bicarbonate into carbonate), or more directly by a rise in either calcium or carbonate.24
After the solid calcium carbonate has appeared in the system by whatever means, precipitation of CaCO3 will begin immediately. What processes inhibit continued precipitation of CaCO3 onto a growing crystal? The main thing happening in normal seawater is likely the impact of magnesium (though phosphate and organics may play an important role in some aquaria).24 This is the point that magnesium gets onto the growing surface of the crystal, essentially poisoning it for further precipitation of calcium carbonate. Since magnesium can reduce the likelihood or extent of calcium carbonate precipitation in this fashion, it thus acts to make it easier to maintain high levels of calcium and alkalinity.
Magnesium limits the formation of calcium carbonate crystals, to the point at which this formation can even stop......if that is the case then calcium carbonate is not forming, which is a problem for corals
This has nothing to do with corals. You are comparing apples and oranges. It is what happens on bare fresh surfaces of carbonate minerals ( gravels), which means high magnesium carbonates are not being formed on the surfaces of fresh carbonate minerals, which means the Mg, Ca and Alk are staying in solution, making it available for corals. Dolomitic gravels will have the highest effect of high Mg calcite precip out on the surface of the dolomite mineral. Pure Calcite will be the least. However, pure dolomite is less soluble than pure calcite. This is may/can be a temporary thing. These surface poisons are very soluble and can/may go back into solution easy. Precip can also happen on heater, glass etc, which is a little different chemistry. Coral biology and their formation of Calcium carbonate is another beast
You are comparing what happens to a bare rock surface to what happens inside a live coral, not the same thing. In a reef tank or even in the ocean this doesn't' happen much, as the gravels get a bacterial surface coating and precip will be nil, if at all. In a new tank it would/may be a temporary thing.You did not read your homework assignment now did you
How does magnesium interfere with precipitation of CaCO3? The primary way involves magnesium poisoning the surface of growing CaCO3 crystals, slowing the precipitation. It can, in fact, be slowed to the point where it simply does not happen at rates problematic to an aquarist. In the following discussion it is important to remember that, other things being equal, alkalinity is a good indicator of the concentration of carbonate. So higher alkalinity equates to higher carbonate.
In short, while magnesium carbonate is not supersaturated in seawater (or in typical reef aquaria), 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 bind.
After a short time in seawater, a virgin calcium carbonate surface quickly attains a thin coating of Mg/CaCO3 (magnesian calcite) as magnesium pushes its way into and onto the crystal surface. Eventually, the surface contains a substantial amount of magnesium. The extent to which this happens depends on the underlying mineral, and is apparently much more extensive on calcite than aragonite. It also depends upon the relative amounts of calcium and magnesium in the water. Regardless, a new type of material is formed that contains both calcium and magnesium.
This new mineral surface containing both calcium and magnesium is not a good nucleating site for precipitation of additional calcium carbonate (as aragonite or calcite), and precipitation of additional CaCO3 slows down substantially.
In Captive Seawater Fishes there is an extensive discussion of the impact of magnesium on the calcium/carbonate system, including a set of data that indicates the magnitude of the impact that magnesium can have.25 In this experiment, batches of artificial seawater were made up with varying magnesium and carbonate levels. The scientists then measured how long it took for calcium carbonate to precipitate from each solution. Not surprisingly, the higher the carbonate was raised, the more rapid was the precipitation of calcium carbonate.
More interestingly, the magnesium levels were found to have a very large impact on the rate of precipitation. In batches with no magnesium, and at natural calcium and elevated carbonate levels, calcium carbonate was found to precipitate in minutes. With a natural seawater level of magnesium added to that mix, the precipitation was delayed to 13 to 20 hours. With double the natural magnesium concentration, the precipitation was delayed to 22 to 29 hours.
Even more strikingly, at a lower level of carbonate (closer to that of natural seawater and probably similar to that in many reef aquaria), precipitation was delayed from a few minutes in the absence of magnesium to 750 hours in the presence of natural levels of magnesium. Consequently, magnesium has a big impact on the rate of precipitation of calcium carbonate (a fact that has been confirmed by many researchers).
But what does that have to do with a reef aquarium? One situation in which calcium carbonate can precipitate involves adding calcium carbonate seed crystals of some type to the aquarium. For example, by adding calcium carbonate sand or one of the calcium carbonate supplements like Aragamight or Kent’s Liquid Reactor.26
A second situation where solid CaCO3 forms is when abiotic precipitation initiates in the aquarium.24 This precipitation happens when supersaturation is pushed to unusually high levels (either in the tank as a whole, or in localized regions). This rise in supersaturation can be caused by a rise in pH (which increases the amount of carbonate present by converting bicarbonate into carbonate), a rise in temperature (as on a heater or pump impeller; the temperature rise decreases the solubility of calcium carbonate and also converts bicarbonate into carbonate), or more directly by a rise in either calcium or carbonate.24
After the solid calcium carbonate has appeared in the system by whatever means, precipitation of CaCO3 will begin immediately. What processes inhibit continued precipitation of CaCO3 onto a growing crystal? The main thing happening in normal seawater is likely the impact of magnesium (though phosphate and organics may play an important role in some aquaria).24 This is the point that magnesium gets onto the growing surface of the crystal, essentially poisoning it for further precipitation of calcium carbonate. Since magnesium can reduce the likelihood or extent of calcium carbonate precipitation in this fashion, it thus acts to make it easier to maintain high levels of calcium and alkalinity.
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mojoreef said:
LMAO too funny..
As for the Salt question I tried to Precip the Mg out of a 5g bucket last night.. Well I dont think that worked.. I think I caused major issues in the bucket LOL... Still cloudy 12hrs later... I think I might have preciptated everything out of there LOL...
I did email Oceanpure about testing some of their salt and what their "Target" levels are..
The basic levels on:
Ca. 400 to 420
Mg. 1100 to 1200
KH 7.5 to 8.2
PH 8.2 to 8.3
The pro series:
Ca. 430 to 450
Mg.1350 to 1450
KH 8 to 9
PH 8.2 to 8.4
Thats what I was told from them... I am hoping they are sending me a sample to test it as well..
James
Well I went to test my 5g test bucket... Pulled it from the tank and threw a PH in there for circulation... I added 6tsp of Baking soda and 1tsp of Washing soda... Whoops overshot.. Good thing Mg preciped out of the water.. from 1500 last night to 1290 this Am LOL.. Water is cloudy.. Alk is thru the roof.. LOL 51.2Dkh.. I wasnt even going to waste the kit to test the Ca... pH was 8.2 in the morning though... LOL.. More than likely its the alk that boosted the pH up though Correct??
James
James
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Yea, the addition of BS and WS (which are bases) shot your pH up to around 12. At this point some Mg salts will drop out. Plus I don't even think BS and WS are that soluble. They are probably sitting on the bottom of the bucket too. Then overnight CO2 dissolved into your water and formed carbonic acid. Then the carb/bicarb and carb-acid all equilibrated and precipitated and the pH dropped closer to the natural solubility and pH of the mixture.
Seriously though. I think you are worried too much of this Mg thing. It doesn't hurt anything to be somewhat off target. Even way off target isn't bad as long as everything is staying in solution. Mg is largely a spectator...not a major player. It mainly just moderates CaCO3 solubility. It does get used some but mainly just because it is laying around.
I wouldn't worry about it if it was me. Your levels are well withing the green range...Collin
Seriously though. I think you are worried too much of this Mg thing. It doesn't hurt anything to be somewhat off target. Even way off target isn't bad as long as everything is staying in solution. Mg is largely a spectator...not a major player. It mainly just moderates CaCO3 solubility. It does get used some but mainly just because it is laying around.
I wouldn't worry about it if it was me. Your levels are well withing the green range...Collin
Illusion said:
Sounds good... I am going to play around with some Salt in a 5g bucket and see if I cant figure some things out... From this time Fwd I am boycotting water changes... only going to add water removed from Monthly frag trades... Just going to have to monitor nitrates and Po4 a little closer... Water changes are Evil LOL... Ca and Alk are right in line so I will just make sure to keep those there... If I boycot water changes anything else I should keep a close watch on? Using ARM media if that helps for the reactor..
James
James
Boomer
Well-known member
Hey Collin, you took away my thunder. I was going to post that.....I was waiting, I guess I waited to long :lol:. I usaully don't give all the info in one post, I like to bait people Hey, its easy to precipitate magnesium. Just use concentrated NaOH and raise the pH to about 12. You'll drop out the Mg all right! or Ca(OH)2,, as you will end up with Mg(OH)2). When you dump kalk in seawater that is the cloud you usually see.
At this point some Mg salts will drop out.
Yes and Ca also
Plus I don't even think BS and WS are that soluble. They are probably sitting on the bottom of the bucket too.
I'll bet on it they will
Hey, its easy to precipitate magnesium. Just use concentrated NaOH and raise the pH to about 12. You'll drop out the Mg all right! or Ca(OH)2,, as you will end up with Mg(OH)2). When you dump kalk in seawater that is the cloud you usually see.At this point some Mg salts will drop out.
Yes and Ca also
Plus I don't even think BS and WS are that soluble. They are probably sitting on the bottom of the bucket too.
I'll bet on it they will
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NaH2O
Well-known member
- Joined
- Jan 25, 2004
- Messages
- 8,568
Wow, great thread! I have to go back and read everyone's reading assignments because I thought I had an understanding and now feel confused (Mike, you better read your assignment....Boomer made it easy for you). When I used Oceanic my Mg was 1525 at corrected salinity of 35 using ATC refract (I'd have to look back at my notes....but my Ca was well over 500). I thought that was what caused the alk to be low. So far what I am understanding from the thread is the high Magnesium isn't that big of a concern. Off for the reading assignments....
Boomer
Well-known member
Just so you know Nikki, Ca @ 400 and Mg @ 1300 really isn't a balance issue. That is just the level in seawater, meaning 1300 is not necessarily the ideal level.
Boomer
Well-known member
I forgot to add to this
However, pure dolomite is less soluble than pure calcite
But, such Dolomites with Hi-Mg Calcites on the surface will go into solution before such poisons on Calcite will, as Dolomite has a greater affinity for Hi-Mg Calcites than Pure Calcite, thus in the long run, the Dolomite is a better "buffer material", but once those nasty bacteria sit in it makes no difference.....
However, pure dolomite is less soluble than pure calcite
But, such Dolomites with Hi-Mg Calcites on the surface will go into solution before such poisons on Calcite will, as Dolomite has a greater affinity for Hi-Mg Calcites than Pure Calcite, thus in the long run, the Dolomite is a better "buffer material", but once those nasty bacteria sit in it makes no difference.....
Ok I didnt get the full monti so I will call that a win!! I must be crazy sitting here in the house of chemistry.
Ok so whip away
MIke
I must be crazy sitting here in the house of chemistry.Ok so what is the corals skeliton??
But I want to play with the oranges to!!,lol
Ok so what does that mean. If you have an 1500 to start with and you continue to do Wc's are you not going to reach a point of saturation?
Ok so in an orange world say??
Ok so whip away
MIke
Yes, a coral skelaton is calcium carbonate with some magnesium and strontium mixed in.
But I want to play with the oranges to!!,lol
Ok so what does that mean. If you have an 1500 to start with and you continue to do Wc's are you not going to reach a point of saturation?
What Boomer is saying is that the corals don't "precipitate" lime. Precipitation is a solubility phenomenon arising from solution phase thermodynamics. Corals "deposit" lime. Although this is chemistry as well, it is moderated by biochemistry. Lots of strange things can happen in cells. In solution, an ion will always flow from local regions of high concentration to areas of low concentration. This is called a "concentration gradient". Ions in solution will always flux down a concentration gradient. In a cell, the cellular mechanisms can actually cause ions to be pumped uphill, or against the gradient. Precipitation is a passive sort of thing. Deposition is a more active phenomena. The coral is basically able to regulate the local concentrations of the ions it deals with (to some extent) via its cellular mechanisms. This is a fancy way of saying its like "apples to oranges".
Also, repeated water changes would not cause magnesium to cycle up. In this case the tank level will always be less than or equal to that of the salt water you perform changes with, all other things being equal. Now if you put salt water into your fresh water top off, that would cycle the ions up.
Make orange juice!
Night...C
Boomer
Well-known member
Collin, I have figured it out. Mikey does not have live corals in his tank he has those dead bleached ones, so now you can see why he is concerned and thus would be correct in that regard Those dead corals would produce an awful lot of fresh carbonate surface areas, that would lower the Ca, Mg and ALk
Those dead corals would produce an awful lot of fresh carbonate surface areas, that would lower the Ca, Mg and ALk
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Ok I will stay out of the orange world. lol
So serious question. Wouldnt the levels of 1500 and 500 make the whole balancing act problematic?? If a person wanted to run their parameters at NSW levels , say at 415 cal, 1290 magnesium and 7-8 dkh what do you do with this salt to make it work??
MIke
So serious question. Wouldnt the levels of 1500 and 500 make the whole balancing act problematic?? If a person wanted to run their parameters at NSW levels , say at 415 cal, 1290 magnesium and 7-8 dkh what do you do with this salt to make it work??
MIke
