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I'm looking to paint my apartment during my three weeks of vacation in September. Unfortunately, my bedroom is way too small to fit the bois' big cage, so I'd have to put them in a temp cage while the paint fumes in the living room subside. Would it be fine to keep them in a smaller temp cage for like a week? And could y'all recommend some good temp cages? I don't trust myself to build a bin cage that they won't be able to break out of.

Additionally, I'd like to expand the main cage by another half cage on top by the end of the year, since my boys will be turning 1 year old and I'd like to add to the mischief to keep it going when my boys grow old and they start to pass on. The cage I have is called "Maximus" and measures 90cm x 60cm x 160cm. I'd like to add another "half" cage on top and build a dig box for them that covers the entire bottom pan. My current cage setup also has two additional full shelves in it, since that's the recommended standard here in Germany in order to offer them sufficient running space. Unfortunately the shelves are quite limiting in regards to offering climbing opportunities.

Would the planned cage expansion suffice for adding another 3 rats to my current 4? Should I keep the shelves or remove them to add more things to climb in there? And if I were to forego the shelves for more climbing opportunities, how best would I go about restructuring the cage to accommodate hind leg degradation, should that become a problem for one of my boys? 

Thank y'all in advance for taking the time to respond.

Questions about temp cage and cage expansions