Made from our Pro-Level Reticulated Foam, specifically suited for colonizing nitrifying bacteria at the highest levels in aquariums.
The current lift-tube color is a dark green. The Slate bottom filters have a round slate attached to the bottom.
As you can see from the list below, a 4.25" cube contains a lot more foam than a 4" one - over 20% more!
The foam you use on these is the good stuff. These are the best bio-filters for the money. I'll be getting more!