Looks like it has K1 media in it, these are getting popular, it's about half full of media. There is am airstone bubbler type thing in there which keeps everything moving. Once BB grows on the media it doesn't float or sink (flinks), water is pumped through the drum. This is a very effecitve bio filtration.
It's like a fludized bed filter with larger media.
It's like a fludized bed filter with larger media.
