i had the martin's topper for my young ones a few years back (gave it to a friend), and i found that the topper's biggest downfall is that the rats kept peeing in the corners of the first level, making the glass sides of the aquarium filthy very quickly, and the only way to clean that kind of thing up is to take the whole thing apart and wipe down the inside of the glass whenever it happens. it's rather inconvenient.