What is this?

[Alec18]

I got a free ten gallon and this was in it. What is it?

 

[Convict2161]

I got a free ten gallon and this was in it. What is it?

Some type media. Was it in the tank or I'm the filter?

 

[Alec18]

Some type media. Was it in the tank or I'm the filter?

Didn't come with a filter

 

[Fishanatic]

Didn't come with a filter

As Convict said, it might be some sort of filter media. That would be a guess, as I don't recall seeing this anywhere.

 

[DannyBWell]

Almost looks like rock maybe?

 

[armymp327]

thats volcanic rock, dont think it should be in an aquarium, i use it for my room to absorb odors such as smoke and what not.

also a link to the product
http://www.containerstore.com/shop/closet/clothingCare/accessories?productId=10008043

 

[Zimmanski]

Seems to me that you could use it in place of bio media in a filter, just like you would ceramic rings. I have a lava rock in my tank as a decoration so I don't know why you couldn't have it