IO salt mix, low Mg and Ca

[mr11]

Hey everyone. Has anyone else had issues with this salt mix? I'm reading Ca of 300 and Mg of 990 on a fresh SW mix. I just started testing Ca and MG and realized they were pretty low. Any recommendation on a salt mix to switch to or any other solution? 

[Origami]

That's lower than advertised, I believe, Ryan. What salinity are you mixing your saltwater up to?

[Origami]

This IO FAQ says that at 1.0264 sg (35 ppt salinity), it should mix up to provide 400 ppm calcium and 1320 ppm magnesium. 

[gmerek2]

Double, and triple check your salinity device. What are you using and do you have calibration fluid?

[mr11]

I mix to 1.026. I use a refractometer that auto adjust to temp. I calibrated with 35ppt solution and also double checked with a specific gravity swing arm meter which was close. Also the salinity measures what the box says it should for mixing 2.5 cups with 5 gallons of RODI water. 

 

I guess it's possible the tests could be bad but I find it pretty unlikely that both tests would be bad and reading so low in error. Unfortunately I have about a years supply of this salt that I bought from a LFS so I'm not really eager to buy more salt to test. Is there such a thing as a "bad batch" of salt? 

[monkiboy]

did you use the entire product or mix the bucket before hand?

[Origami]

 Also the salinity measures what the box says it should for mixing 2.5 cups with 5 gallons of RODI water. 

Just to note: IO's recommendation for 1/2 cup per gallon of water does not mix up to 1.0264 (35 ppt). Instead, that's the formula to get you to 1.022 sg (or 29.2 ppt). At that ratio, you an expect calcium to be at 400*29.2/35 = 333 ppm and magnesium at 1100 ppm. 

 

Another note: The ratio of your magnesium to calcium is 990/300 (or 3.3) which is consistent with IO's target values of 1320/400 (3.3) when mixed to 35 ppt. Because of this, I suspect that you're mixing to a diluted solution actually.

[mr11]

did you use the entire product or mix the bucket before hand?

 

The entire salt product? I can only mix 5 gallons at a time unfortunately so I have a lot of salt I still haven't used. 

 

 

Just to note: IO's recommendation for 1/2 cup per gallon of water does not mix up to 1.0264 (35 ppt). Instead, that's the formula to get you to 1.022 sg (or 29.2 ppt). At that ratio, you an expect calcium to be at 400*29.2/35 = 333 ppm and magnesium at 1100 ppm. 

 

Another note: The ratio of your magnesium to calcium is 990/300 (or 3.3) which is consistent with IO's target values of 1320/400 (3.3) when mixed to 35 ppt. Because of this, I suspect that you're mixing to a diluted solution actually.

 

Interesting. Just double checked the box and it says 1.022-1.024. I double checked and recalibrated the refractometer and I'm still getting 1.026. Used a hydrometer which gave me 1.025. 

 

The ratio is the same but the value is still 75% of what it should be. I haven't done the exact math but it doesn't seem like the amount of salt needed to raise salinity from 1.022 to 1.026 would be enough to account for a 25% difference in Mg and Ca. According to a previous thread on here actually Ca should be 361 and Mg should be 1264 at 1.022 but I'm not sure how accurate that is. 

 

Anyway, I feel like there must be something obvious I'm missing but all of my backup checks are reinforcing my initial readings. So I'm lost. Do LFS around here do full parameter tests including Ca, Mg, Alk etc? 

Edited January 29, 2016 by mr11

[monkiboy]

The entire salt product? I can only mix 5 gallons at a time unfortunately so I have a lot of salt I still haven't used.

roll/gently shake the bucket/bag the salt before use. settling can affect your results quite a bit.

[Jason Rhoads]

roll/gently shake the bucket/bag the salt before use. settling can affect your results quite a bit.

I have seen others discuss this exact phenomenon. Unless you use the entire bag there may be inconsistencies (probably even variances from bag to bag).

[mr11]

roll/gently shake the bucket/bag the salt before use. settling can affect your results quite a bit.

 

 

I have seen others discuss this exact phenomenon. Unless you use the entire bag there may be inconsistencies (probably even variances from bag to bag).

 

Hm well that's interesting. I'll give that a try. I just finished a bag so I'll shake up the next one and retest. 

[Origami]

I did the math for you above. The math indicates that it's possible that you may be mixing to less than 29.2 ppt salinity.

You actually need almost 20 percent more salt to go from 1.022 sg (which is 29.2 ppt) to 1.0264 (35 ppt).

Salt manufacturers play with us that way. For example, a 200 gallon box of IO mixes up to roughly 167 gallons at 1.0264. A 200 gallon box of Reef Crystals nets 160 gallons as I recall.

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[mr11]

I did the math for you above. The math indicates that it's possible that you may be mixing to less than 29.2 ppt salinity.

 

You actually need almost 20 percent more salt to go from 1.022 sg (which is 29.2 ppt) to 1.0264 (35 ppt).

 

Salt manufacturers play with us that way. For example, a 200 gallon box of IO mixes up to roughly 167 gallons at 1.0264. A 200 gallon box of Reef Crystals nets 160 gallons as I recall.

 

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What you're saying makes a lot of sense to me and seems to be the simplest answer. But for that to be true it would mean my refractometer/calibration fluid and swing arm hydrometer are all wrong in exactly the same way, so that they all agree with each other. I need to get it tested at a LFS. 

[Origami]

Yes. It would be good to cross-check. I'm just offering up another alternative to look at. I find it very interesting that the Ca:Mg ratio is exactly as it should be, but that the absolute concentration is low. It's also possible that you have a poorly mixed bucket of salt. It has been known to happen. And finally, it's rare, but there have been bad batches of salt released at times. The last time I remember that happening was about 5 or 6 years ago, though.

 

I routinely cross-check measurements with different kits especially if I'm planning on re-balancing my chemistry. The cross-checking helps to identify a bad kit sometimes. Just a week ago, I had some Hanna alk reagent give me really bad (high) numbers. Yeah, I just heard about the recall - but a quick look at the bottle showed that the reagent had expired a few months ago. After grabbing another bottle, the numbers fell back into line, aligning with my Salifert and Red Sea Pro kits.

[astroboy]

I had a problem with low salinity which origami helped me with, as I recall. It was a few years back, I can't recall what I had for breakfast.

 

Basically, with cooler water, you get a higher salinity reading with a refractor for X amount of salt. This is because the index of refraction for cooler (or hot) water changes significantly with temperature. My water was at about 50 degrees (mixing it in a shed outside) and my accurately calibrated refractometer showed 35ppt, after four days of agitating and aerating. I'd put the water in 7 gallon plastic jugs and heat it to 80 degrees when I did water changes. But,at that point the refractor showed maybe 30 ppt, if that much. I waited a couple of minutes for the water on the refractor meter to reach the same temp as the refractometer, it was a good measurement. 

 

For an accurate measurement of salinity with a refractometer, you need both the water and the refractometer to be pretty close to the temperature of your tank.

 

Even mixing in my basement, which is about 65 degrees, I get a big change in salinity reading, maybe 32 vs 35 ppt. I don't recall. 

 

For hydrometers, I'm not sure what the effect would be since I'm not sure how much the density of water changes with temperature. However, since index of refraction is basically a measure of density of electrons in a liquid (so I'm told) I'm betting even a hydrometer would give bogus results in cold water. You'd  also have to deal with the contraction of the glass at cold temps, another questionable quantity. 

[mr11]

Thanks everyone. I really appreciate all of your help so far. My plan is to get my water tested at a LFS and depending on what they say, pick up some Reef Crystals. If my numbers are reading way low compared to what the LFS says I'll assume there is an error in my testing. If not, I'll assume it's a poorly mixed bag or the mix is just "off" for whatever reason. I'll get some reef crystals and repeat the experiment (after mixing/shaking the bag) and see if I get better numbers. If I do, and my tests are accurate, I'll dose some Ca and Mg supplement to bring my numbers up as a short term solution and switch to reef crystals for a long term solution. I'm curious to see how this goes. 

Edited January 29, 2016 by mr11

[Origami]

Thanks everyone. I really appreciate all of your help so far. My plan is to get my water tested at a LFS and depending on what they say, pick up some Reef Crystals. If my numbers are reading way low compared to what the LFS says I'll assume there is an error in my testing. If not, I'll assume it's a poorly mixed bag or the mix is just "off" for whatever reason. I'll get some reef crystals and repeat the experiment (after mixing/shaking the bag) and see if I get better numbers. If I do, and my tests are accurate, I'll dose some Ca and Mg supplement to bring my numbers up as a short term solution and switch to reef crystals for a long term solution. I'm curious to see how this goes.

Please report back. I normally mix up at least 40 gallons at a shot so mixing normally isn't much of an issue. It's a reminder that we should all test our change water from time to time, and not only our tank water.

 

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[AlanM]

Good reminder for me as well with the current uncertainty about the Hanna Alk checker.  I've had really high Mg for a while and very well may be overshooting on the salinity since I test that infrequently.

[EBR]

I love this hobby.  It's great.  Except those moments when I feel like I've been everything wrong for 10 years!  

 

from Tom/Oragami> Just to note: IO's recommendation for 1/2 cup per gallon of water does not mix up to 1.0264 (35 ppt). Instead, that's the formula to get you to 1.022 sg (or 29.2 ppt). At that ratio, you an expect calcium to be at 400*29.2/35 = 333 ppm and magnesium at 1100 ppm. 

 

and> You actually need almost 20 percent more salt to go from 1.022 sg (which is 29.2 ppt) to 1.0264 (35 ppt).

 

And so for me, those early habits grew deep roots, I suppose, because that is exactly what I have been following, the darn instructions on the IO bucket.  I have been targeting 1.022 salinity and the Ca is exactly in the 340-ish range.  No wonder my LPS growth has seemed to go backwards.

 

</end self pity>

 

So, I take it then that instead of the 2.5 cups of IO per 5 gallons of RODI I have been mixing, I would be better off with 3 cups (adding 20%) to target a SG of 1.026?

 

Thanks so much, this thread is bookmarked ;-)

 

Matt

[Origami]

Matt, you should always check the salinity of your change water when you've mixed it. It's just good practice.

 

To get nit-picky, salinity is measured as a weight ratio, not a volume ratio. So, IO's (and other salt's) recommendation of 1/2c per gallon is intended to get you close to 1.022 sg (or 29.2 ppt). The actual detailed and accurate instruction would tell you to add x grams of salt mix to y grams of water. However, nobody normal is in a position to weigh their salt mix and water, so IO provides a volume-based guideline that's good for practical purposes.

 

That said, assuming that weight and volume scale pretty closely for the salt mix (and it should), then to mix to 35 ppt you'll need to scale the salt mix added by 35 divided by 29.2, which is 1.2.  So, yes, 2-1/2 cups becomes 2.5 x 1.2 = 3 cups to mix up a 5 gallon batch to 35 ppt.

[EBR]

Outstanding -- thanks so much.  

Matt

[mr11]

SO

 

I took in some water to get tested today. They use Salifert just like me.

 

Salinity 1.026

Alk 8.1 dKH

Ca 380

Mg 1230

 

Much better numbers than I got. I purchased a new Salifert Ca kit (they didn't have Mg unfortunately) and just tested with the new kit and got 380 as well. 

 

I guess both tests were bad in the perfect way. To both give low readings while maintaining the expected Ca/Mg ratio. I thought it might be user error so I had the guy at the LFS show me how he tested. It was no different than how I was using the kits and how I retested when I got home today.

 

The numbers are still a little low so I decided to transition to Reef Crystals anyway. To transition should I just start doing water changes with the new salt? 10% of water volume at a time?

 

Make sure to double check those test kits we all rely on so much every once and a while. Had I made decisions based on the numbers I was initially getting I could've caused some serious harm.  

[AlanM]

Yes. I would just start doing water changes with the new salt. 

[Origami]

Glad that you got it figured out. Bad test kit readings are common. It's uncommon, though, to have two kits off by the same proportion. You just got lucky, I guess. 

 

I normally keep two or three different manufacturer's test kits around for the common tests just to cross-check when I get numbers that are suspect.