Does GAC introduce phosphates?

[pw9988]

I have my phosphates at .17ppm and phosguard is not lowering it. I have it in a media bag mixed with GAC. I called Seachem for advice and troubleshooting and they mentioned that GAC is a source of phosphates, however, I couldn't find any info online that backs this up. Has anyone else heard the same? If it's true, this would explain why I do not see my phosphate levels decreasing.

 

[Spare time]

Carbon can release some phosphates (I am not sure of the mechanism though). Typically it is a problem with the really low quality carbons.

 

[Montiman]

The hard thing with any, "Will this add Phosphate?" question is that almost everything has phosphate in it. DNA has a phosphate backbone as part of its structure so pretty much anything organic has some phosphate in it. I have never seen any aquarium have high phosphates because of carbon use. However very low quality coconut carbon is often rinsed in phosphoric acid in manufacturing. This could be a problem, but I do not currently know of any brand of aquarium carbon that is such a low grade product currently.

 

[pw9988]

So the one I had in there (removed after the phone call with Sea Chem) is MarineLand Diamond Media Premium Activated Carbon. Good reviews on Amazon, however, it was purchased for scrubbing the air within an enclosure for a 3d printer. I also have BRS ROX. What I'll probably do is weigh some of each out, mix it with RODI and let it sit over night and test if either of the two GAC samples released any phosphates.

 

[Spare time]

The ROX will not release detectable phosphate. I am not sure about the marineland but the manufacturer should have a phosphate output number.

 

[pw9988]

It looks like it might just be a bad batch of phosguard. I swapped the media over to GFO. Used the 5" cartridge from BRS, and shoved that into the filter basket. Couple hours later, I'm down to .05 ppm phosphate from .17

Seachem is supposed to get back to me after they test the lot number that my bucket of Phosguard came from.