Choosing Bedding
Here are some of the options available for rat bedding and my opinions on them.
Shredded paper
Most shredded paper (e.g. from your home office) is fine to use for rat bedding. Paper that has been printed on with toxic ink should be avoided as rats will attempt to eat most bedding. Shredders that cut longer strips of paper are more suitable as shorter (or cross cut) shreds are very fly away and aren’t as good for building extravagant nests. Shredded paper can also be quite dusty (a by product of the cutting process) so it may be worth avoiding for rats with known respiratory problems. Shredded paper is also pretty poor in absorbency which can lead to smelly rats if you have rats that insist on urinating in there bed.
Shredded tissue/J cloth bedding

shredded tissue bedding
This covers the main 2 commercially available small animal bedding. Both have similar absorbency (though the J cloth bedding is slightly better) and are similarly insulating. The J cloth bedding is pretty rubbish structurally but can be popular to line big newspaper nests and the shredded tissue can be good depending on the length of the strips (the longer the better for nest builders).
Paper towels
This is primarily sheets or strips of kitchen towels. They seem very popular with rats and are reasonably absorbent and can be structural. They do tend to get a bit smelly (as with all paper based nesting material) after a few days of lazy rats urinating in there beds but it’s often nice to throw a couple of sheets in for the rats to tear or play with. An alternative to this and much appreciated by the rats is to pop in a cheap roll tied to the bars and let the rats dispense there own. It will result in a cage full of paper towels but the rats will love it.
Material
This is generally the most absorbent and insulating bedding. It’s usually off cuts of fleece or towels (from hammock making) and is my preferred choice for bucks for these reasons, unfortunately it’s a bit heavy to make proper nests out of so I’d tend towards the shredded paper for nest enthusiasts.
News Paper
This is a popular rat bedding, especially as nearly all newspaper in the UK is now printed with vegetable inks (none toxic). Rats, especially manic nest building girls, seem to love newspaper over pretty much all other beddings as it can be torn and carried very effectively. Placing a pile of roughly torn up news paper in a corner will let the rats distribute it where they like or alternatively provide a few sheets folded up and let the rats tear there own. This is a cheap (often free) nesting material and whilst it isn’t great on the absorbency front, if changed every few days is a popular option especially as it is highly structural and makes good nests.
Cotton wool bedding
This is traditionally sold as hamster bedding and provides a nice warm insulating nest. However as rats are almost always kept in groups and so are less likely to need such insulating nesting material. This bedding has also been known to get caught round toes and ingested so it is definitely worth avoiding.