It doesn't have one of those. It's a very simple filter. For now, I have the sponge filter in. I was torn between having it, since it makes alot of bubbles and Lapis doesn't like those, or not having it and risking the junk to build up over 5 days. I've been watching him and he seems ok with it now, cruising around.
On the other hand, if I knew 5 days without a water change wasn't going to kill him, I'd prefer to leave the bubbles off to keep it calmer. But, my gut tells me to have at least some kind of filter going...