How much Will salinity effect major elements?

Rubblereefer

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Around what percent would mag/alk/Ca raise per point of salinity? Real world example, I tested my Mg last night, its at 1155, too low. I then tested salinity, and it is also too low at 1.024. Rather than add magnesium, I will let the salinity come up by a point or two. Im just wondering around what the Mg DKH and CA will raise up to when I raise the salinity to lets say 1.026. Is there a general rule of thumb, like 10% per point for example?
 
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Rubblereefer

Rubblereefer

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A difference between 1.024 and 1.026 is around 7% percent depending on how you calculate it. based on converting SG to ppm. Why not just measure the Mg? ps - this percentage will not match if you go from 1.010 to 1.012 for example
Thank you that was exactly the info I was looking for. I will certainly measure the Mg level when the tank reaches 1.026, but now I know that I can expect around 1235 using that formula. Sounds like DKH would raise about .5 which is also fine. When I get to 1.026 I will remeasure and post the result for others future reference.
 

Kriz

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Changes in parameters with increasing salinity will directly depend on the salt manufacturer. Different salt will increase your calcium, alkalinity, magnesium in different ways.
 
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MnFish1

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Changes in parameters with increasing salinity will directly depend on the salt manufacturer. Different salt will increase your calcium, alkalinity, magnesium in different ways.
I think you are missing the point. No - they will not . If the salinity increases by x percent - the others will increase the same percent. With 1 salt vs another, the starting point might be different, but the change will be the same. The easiest way - is to just measure the Mg, etc directly, when increasing the salinity. (the OP was going to increase the salinity just by letting it evaporate) - thus the percentage is important not which salt he was using
 

wilsonline

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Not sure if I was clear.
31.9/34.5= 1155/x ---> x= 1249 ppm of mag.
At 35 ppt you would have a decent value of 1270 ppm of mag. Sounds great with the math, just not sure how detrimental this variation in salinity could be to corals. Maybe just ok if done in a period of around a week. idk
That 31.9 would be the concertion of your salinity in sg (1.024 sg) to ppt (31.9 ppt). same with the other numbers. I prefer to use ppt unit to salinity.
So, increasing salinity from 31.9 to 35 ppt, you should get your mag at 1270 ppm which is a better value for mag.
Very simple math.
Just divide your mag (1155 ppm of mag) value to your salinity (1.024 sg less the 1.0 part or just convert to ppt). Then, divide your current salinity (less the 1.0) to where you will bring it. So 26/24 (31.9/34.5 ppt) = 1.082. then, multiply that (1.082) by the original value of mag. 1.082 * 1155 = 1249 ppm of mag. With same math, you will find 1270 ppm of mag at 35 ppt.
 

MnFish1

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Not sure if I was clear.

That 31.9 would be the concertion of your salinity in sg (1.024 sg) to ppt (31.9 ppt). same with the other numbers. I prefer to use ppt unit to salinity.
So, increasing salinity from 31.9 to 35 ppt, you should get your mag at 1270 ppm which is a better value for mag.
Very simple math.
Just divide your mag (1155 ppm of mag) value to your salinity (1.024 sg less the 1.0 part or just convert to ppt). Then, divide your current salinity (less the 1.0) to where you will bring it. So 26/24 (31.9/34.5 ppt) = 1.082. then, multiply that (1.082) by the original value of mag. 1.082 * 1155 = 1249 ppm of mag. With same math, you will find 1270 ppm of mag at 35 ppt.
Sorry but this is a confusing mess. You cannot just 'take off' the 1.0 part. Maybe its just the wording. The BEST thing to do is to just measure the Mg at whatever salinity you end up with. Again I'm not trying to make this more confusing that you've made it - but to me this makes no sense: "So 26/24 (31.9/34.5 ppt) = 1.082." - I think I get what you're trying to say - key point - you can't equate every 2 point change in SG with x percent change in Mg.
 

Kriz

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I think you are missing the point. No - they will not . If the salinity increases by x percent - the others will increase the same percent. With 1 salt vs another, the starting point might be different, but the change will be the same. The easiest way - is to just measure the Mg, etc directly, when increasing the salinity. (the OP was going to increase the salinity just by letting it evaporate) - thus the percentage is important not which salt he was using
The two easiest ways to increase water salinity are:
1. Add salt.
2. Evaporate the water.
But, using the evaporation of water, OP will need to compensate for the evaporated water with salt water. While the water evaporates, all indicators will change proportionally. Next, it will be necessary to add salt water, the volume of which will be equal to the volume of evaporated fresh water. It is difficult to predict how the indicators of calcium, alkalinity and magnesium will change, since we have no idea about the composition of the added water.
Where am I wrong?
 

Randy Holmes-Farley

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Sorry but this is a confusing mess. You cannot just 'take off' the 1.0 part. Maybe its just the wording. The BEST thing to do is to just measure the Mg at whatever salinity you end up with. Again I'm not trying to make this more confusing that you've made it - but to me this makes no sense: "So 26/24 (31.9/34.5 ppt) = 1.082." - I think I get what you're trying to say - key point - you can't equate every 2 point change in SG with x percent change in Mg.

You pretty much can do that.

If sg = 1.024 and you want to know the value of a concentration if you allowed evaporation to take the sg to 1.026, you multiply any existing value by 26/24 (1.083).

So if magnesium is 1155 ppm and you allowed evaporation to increase the SG, magnesium becomes 26/24 x 1155 = 1251 ppm
 
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MnFish1

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You pretty much can do that.

If sg = 1.024 and you want to know the value of a concentration if you allowed evaporation to take the sg to 1.026, you multiply any existing value by 26/24 (1.083).

So if magnesium is 1155 ppm and you allowed evaporation to increase the SG, magnesium becomes 26/24 x 1155 = 1251 ppm
So - yes - I just said the way it was worded confused me. Isn't the easiest thing to just measure that Mg? Which likely - he/she would do anyway? - And - the difference in my tank between lets say a Mg of 1200 and 1300 would be 'none' of significance to the inhabitants. Its just my opinion - people are 'pretending' (no criticism, no offense) - that a Mg of 1248 is really 'that value' - s compared to 1270 or 1230, etc.
 

MnFish1

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The two easiest ways to increase water salinity are:
1. Add salt.
2. Evaporate the water.
But, using the evaporation of water, OP will need to compensate for the evaporated water with salt water. While the water evaporates, all indicators will change proportionally. Next, it will be necessary to add salt water, the volume of which will be equal to the volume of evaporated fresh water. It is difficult to predict how the indicators of calcium, alkalinity and magnesium will change, since we have no idea about the composition of the added water.
Where am I wrong?
I have no clue - reading this - what you're actually trying to say. UNLESS - its this. Lets say you have 100 gallons of salt water - and 1 gallon evaporates (resulting in an increased salinity). If you replace it with 1 gallon of 'RODI' you will end up the same. So - you need to replace it with 'new mixed saltwater'. I think thats what you're saying. I also agree - you cant predict the Mg to the accuracy in the calculation mentioned above - due to the margin of error in the tests. I would adjust the salinity (how ever you want) - and then measure the other 'stuff' and adjust them as needed (Ca, Alkalinity, Mg). I think we are on the same wavelength. My main point was don't try to predict - just measure.
 

drnibz

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Not sure if I was clear.

That 31.9 would be the concertion of your salinity in sg (1.024 sg) to ppt (31.9 ppt). same with the other numbers. I prefer to use ppt unit to salinity.
So, increasing salinity from 31.9 to 35 ppt, you should get your mag at 1270 ppm which is a better value for mag.
Very simple math.
Just divide your mag (1155 ppm of mag) value to your salinity (1.024 sg less the 1.0 part or just convert to ppt). Then, divide your current salinity (less the 1.0) to where you will bring it. So 26/24 (31.9/34.5 ppt) = 1.082. then, multiply that (1.082) by the original value of mag. 1.082 * 1155 = 1249 ppm of mag. With same math, you will find 1270 ppm of mag at 35 ppt.
This assumes the change in Mg is linear to the change in salinity. I don't believe that
 

wilsonline

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This assumes the change in Mg is linear to the change in salinity. I don't believe that
I might be wrong, but I believe it's linear or very close to linear. So that we can calculate that difference in mag considering it linear.
I have no clue - reading this - what you're actually trying to say. UNLESS - its this. Lets say you have 100 gallons of salt water - and 1 gallon evaporates (resulting in an increased salinity). If you replace it with 1 gallon of 'RODI' you will end up the same. So - you need to replace it with 'new mixed saltwater'. I think thats what you're saying. I also agree - you cant predict the Mg to the accuracy in the calculation mentioned above - due to the margin of error in the tests. I would adjust the salinity (how ever you want) - and then measure the other 'stuff' and adjust them as needed (Ca, Alkalinity, Mg). I think we are on the same wavelength. My main point was don't try to predict - just measure.
I guess he noticed his mag was low, checked his salinity and it was low as suspected. After all, mag is a major element that isn't consumed as fast as others like carbonates. soooo, he asked if he could calculate it that way and how to do it. After all, he would be raising his salinity, and maybe there was no reason to dose mag if the future value was going to be ok. In that case, I would double-check. If that value is correct (crazy tests), maybe I would dose 100 ppm to be higher ( I target 1350 ppm mag), but only if I already had mag supplement at home. IDK, but 1250 should still be ok.
I may be wrong, but always that I see a weird value of mag, I check or suggest checking salinity or the salt mix.
 

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