Aquariums are not appropriate cages for rats at all, just to add in. They're very prone to respiratory problems, and the ammonia buildup that's possible in an aquarium, even a very clean one to human noses and hands, is dangerous to them and may trigger respiratory infections and other problems.
A nice, well-ventilated wire cage of an appropriate size is a much better choice. Even with the aquarium topper, you're making a glass fumigation box of ammonia at the bottom!
We are as gods to the beasts of the fields. We order the time o' their birth and the time o' their death. Between times, we ha' a duty. - Terry Pratchett.
"Men have forgotten this truth", said the fox, "But you must not forget it. You become responsible, forever, for what you have tamed. - Antoine de Saint-Exupéry