Very High Sulfate ICP-MS result

[Formulator]

Just got my latest ICP-MS results back from Oceamo. Most things looked good, except significantly elevated sulfate, reported as 3734 mg/L.

First, are there any reports of negative impact on reef organisms? I’m not finding much, but the other examples I’ve found aren’t quite as high as my result.

Second, any ideas about the source of sulfate? I did do a magnesium correction a couple months ago using BRS general mag adjust which I believe is a mixture of MgCl and MgSO4. Otherwise, daily dosing consists of Randy’s DIY 2-part recipe with unbaked baking soda, NeoNitro, and Reef Moonshiners Manganese (0.5 mL), Selenium (0.1 mL), Cobalt (0.1 mL), Chromium (0.1 mL), and SeaChem Iodine (0.1 mL). 130 g total system volume. I use reef crystals salt.

 

[PharmrJohn]

Well, your Mg²SO4 is an ionic compound. It easily cleaves to produce two Mg cations and one SO4 (Sulfate) anion. I would guess that's where at least some of it is coming from. I looked it up and SO4 is a major anion present in seawater. What your levels mean to your tank is not known to me, but it is abundant naturally.

 

[Randy Holmes-Farley Verified Community Expert]

Just got my latest ICP-MS results back from Oceamo. Most things looked good, except significantly elevated sulfate, reported as 3734 mg/L.

First, are there any reports of negative impact on reef organisms? I’m not finding much, but the other examples I’ve found aren’t quite as high as my result.

Second, any ideas about the source of sulfate? I did do a magnesium correction a couple months ago using BRS general mag adjust which I believe is a mixture of MgCl and MgSO4. Otherwise, daily dosing consists of Randy’s DIY 2-part recipe with unbaked baking soda, NeoNitro, and Reef Moonshiners Manganese (0.5 mL), Selenium (0.1 mL), Cobalt (0.1 mL), Chromium (0.1 mL), and SeaChem Iodine (0.1 mL). 130 g total system volume. I use reef crystals salt.

Miami ran into this issue when BRS changed materials to anhydrous magnesium sulfate but he didn’t know it so kept using the original recipe.

 

[Randy Holmes-Farley Verified Community Expert]

I’ve not seen data suggesting a problem (or not a problem).

 

[Christoph]

Hello!

It is very difficult/unlikely to achieve such a high sulfate value by dosing, even when magnesium is dosed using magnesium sulfate. A possible reason can be the use of sulfur denitrators, but i guess you are not running such a device.

We do find very few cases of high sulfate in EU reef tanks, but its something quite common in US tanks. For me the most plausible cause is that certain salts (or certain batches of a salt) available on the US market have a higher sulfate content. It would be interesting to conduct analyses on freshly made saltwater.

BR,
Christoph

 

[Formulator]

Well, your Mg²SO4 is an ionic compound. It easily cleaves to produce two Mg cations and one SO4 (Sulfate) anion. I would guess that's where at least some of it is coming from. I looked it up and SO4 is a major anion present in seawater. What your levels mean to your tank is not known to me, but it is abundant naturally.

Yep, I’m a chemist professionally ;). The Mg adjust was my initial thought as well, but the math doesn’t work out even if that BRS mix was 100% MgSO4. I would be looking at maybe 500 mg/L SO4 increase from that. But I’m 1000 mg/L over target.

I’m thinking perhaps my salt mix, or from letting my RODI filters go unchanged for almost 3 years during my infamous period of neglect. I’ve changed about 150 gallons during my tank rehabilitation over the last 7 months, but who knows how high it got.

 

[Formulator]

It is very difficult/unlikely to achieve such a high sulfate value by dosing, even when magnesium is dosed using magnesium sulfate.

To me it doesn’t seem so far out of the realm of possibility… a 150 ppm adjustment of magnesium with magnesium sulfate would equate to about 600 ppm sulfate increase, if my math is correct. I had to rehabilitate my tank at the beginning of this year after a long period of neglect and made an adjustment of 150 ppm. I thought I was using a mixture of MgCl and MgSO4, but perhaps the supplier made an error with the recipe as @Randy Holmes-Farley mentioned.

 

[Formulator]

@Miami Reef ?

 

[Randy Holmes-Farley Verified Community Expert]

https://www.reef2reef.com/threads/chloride-lower-and-sulfur-too-high-icp.1044458/

 

[Formulator]

https://www.reef2reef.com/threads/chloride-lower-and-sulfur-too-high-icp.1044458/

I see what you meant now. I thought you were saying BRS messed up a batch of their solid mix. I mixed my mag adjust solution per the BRS instructions so not sure that is the culprit here.

 

[Miami Reef]

@Miami Reef ?

I used magnesium sulfate anhydrous but with a recipe meant with Epsom salt.

I also used the ratio for two parts instead of the ratio for general dosing. The 10:1 is the correct ratio for systems using Balling Part C.

 

[Miami Reef]

For me the most plausible cause is that certain salts (or certain batches of a salt) available on the US market have a higher sulfate content. It would be interesting to conduct analyses on freshly made saltwater.

https://www.reef2reef.com/threads/oceamo-icp-ms-results-for-instant-ocean-batch-23108.992762/
Of course, there might be variations between batches, but I haven’t seen an elevated sulfate issue in instant ocean purple (the salt I used).