Good job on the initial cage set up! Over the years I’ve come to the personal conclusion that a cluttered cage is a happy cage. (Your first cage is much better than my first cage was, by the way!) This doesn’t mean it should be crammed so full that ratties cannot move, but the more items they can chew, shred, hide in and climb on, the better. As prey animals rats appreciate places where they have lots of options to hide, are they are very adept at maneuvering in and around things. Having a lot in a cage also encourages natural behaviors like climbing in and on and around, stashing food and building nests. Plus it’s a treat to watch them play “hide and seek.” It doesn’t have to be anything fancy or store bought — you already have some great homemade things in there, like discarded cardboard boxes that make great forts if you cut a few holes for rats to enter/exit. They can also be put end to end to make longer rows of houses, or stacked with holes between to make “buildings” several stories high. Old soft clothing (like tee shirts, sweats, etc) can be turned into bedding by cutting it into strips, or taking the sleeves or pant legs, attaching them to the sides of the cage and making hanging tunnels for ratties to climb through. The more they have to interact with and explore, the safer and happier they tend to be. Good luck, and enjoy your ratties!