ok. Most people who buy those types of cages end up covering the floor with something else. Right now I am setting up a Martin's cage for my hamster (still in the works) and I am going to line the floor with puzzle playground pieces to prevent her from falling through the holes like that. They can walk on those spaces, but they can also slip through them and get caught and hurt themselves. Depending on the set-up of this topped you might be able to do something more solid, like plexiglass or even just tie some sort of cloth over it.