Never used one but my general feelings on it are this.
1. Seems kind of small, maybe good for 10g? little under 2" dia with just over that in length doesnt leave a horrible amount of sponge space for growing bacteria.
2. all major components needed appear to be there, seems like it should function just fine, again wouldnt really suggest it for much larger than a 10g.
3. Just from a designer standpoint, that clear tube part is worthless, it should have been made with pure black plastic, less light = less algae inside of the tube.