Housing
Floor space and ventilation matter more than height or accessories.
Cage choice
Wire cages ventilate far better than glass tanks, which trap ammonia at floor level where the animals breathe. Bar spacing must be small enough that a mouse cannot slip through — they fit through gaps that look impossibly narrow.
Rats need climbing height and solid shelves; wire floors cause foot injuries.
Bedding
Paper-based bedding and aspen are the usual safe choices. Cedar and untreated pine shavings release aromatic compounds that irritate rodent airways and are best avoided.
Spot-clean often and fully clean on a schedule: ammonia build-up is the most common cause of respiratory disease in these species.
Enrichment
A solid-surface wheel of the right diameter, cardboard to shred, and places to hide. A wheel that is too small forces the spine into a curve and does more harm than good.