Why not just use bedding to cover the bottom? That way you can simply replace bedding as needed, it might be easier. When I had degus I ended up using Yesterday's News (and similar brands) litter in the bottom tray, it was easy to clean

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But if you don't think she's scared, I don't see a problem. Maybe do it when she's out of the cage so there's no risk of her freaking out

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A bowl is fine but it should be very heavy since degus love tipping things over. I would still have the
water bottle there as an option just in case, though

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