What Exactly Is This??

I recently bought a used tank at a pawnshop to use as a quarantine tank. It had a few typical supplies in it, but this one thing I’ve never seen before. It looks similar to cat litterbox gravel inside a mesh bag. Anyone know what it is?? TY!

 

It looks like filter media- media used to culture/grow helpful bacteria.

 

It's Seachem Purigen!

 

Don't think it's purigen. Purigen stuff is a bit finer than that. Looks like ammonia removing media to me. I personally wouldn't use it regardless what it really is.

 

looks like garbage . It does look like the ammonia reducer I've seen, I wouldn't use any used filter media if I didn't know where it came from.