Magnesium with giant crystals?

[CHSUB]

New container with giant crystals? What is going on here…

 

[Baldyreef]

seems like it is just crystalized, as long as there's no contaminants it should just be crystals that can be crushed and used like normal

 

[Randy Holmes-Farley Verified Community Expert]

I'm not a fan of Seachem Reef Advantage Magnesium.

It has an odd way of attaining sulfate/chloride balance by making the product mix from Epsom salt (magnesium sulfate) and sodium chloride. They have long worried about ammonia in magnesium chloride, so do not use it.

https://www.seachem.com/reef-adv-magnesium.php
Ingredients: magnesium sulfate, sodium chloride

With that as a backdrop, I don't see how that product could reasonably exist as large single crystal chunks, and it makes me suspicious about what the product actually is in the bottle.

Are there little crystals present, like table salt?

 

[CHSUB]

I'm not a fan of Seachem Reef Advantage Magnesium.

It has an odd way of attaining sulfate/chloride balance by making the product mix from Epsom salt (magnesium sulfate) and sodium chloride. They have long worried about ammonia in magnesium chloride, so do not use it.

https://www.seachem.com/reef-adv-magnesium.php
Ingredients: magnesium sulfate, sodium chloride

With that as a backdrop, I don't see how that product could reasonably exist as large single crystal chunks, and it makes me suspicious about what the product actually is in the bottle.

Are there little crystals present, like table salt?

It is like broken glass. If I rinse, it gets clear and slowly dissolves.

 

[CHSUB]

Could it be epson salt? Looks similar?

 

[Randy Holmes-Farley Verified Community Expert]

It could be either the Epsom salt, or large chunks of sodium chloride, but if all the chunks seem similar, it seems unlikely to include both.

 

[Randy Holmes-Farley Verified Community Expert]

FWIW, a proper ionic balance this way needs much more sodium chloride than Epsom salt by mass. More than 6:1.

 

[CHSUB]

From Seachem:

Support FD (Seachem Laboratories) Aug 24, 2026, 17:59 ADT Hello, These crystals are actually sodium chloride, an ingredient of this product, and it is just fine to use! We just recommend dissolving any chunks in water before adding to the tank. Please note: This bottle is of an older batch made in 2022. In 2024, we changed to a smaller grain size of the sodium chloride. Best regards, FD

 

[Randy Holmes-Farley Verified Community Expert]

Do you see smaller grains too?

 

[CHSUB]

Yes, small crystals are about 80% of product.

 

[Randy Holmes-Farley Verified Community Expert]

Ok, thx. :)