I have seen some of your use the paper from a shredder, and i was wondering if it is safe...if there is ink, wont it be poisonous for them? I' wondering because my mom has a ton of paper from her shredder and she wanted to know if id like it for my mice.
Any state/city sanctioned Newspaper in the US is required by law to use non-toxic ink.
Penny-dimes, and little local publishing, fliers and whatnot may or may not use non-toxic ink, and the same goes for junk-mail, so I would not use these as substrate. You also have to watch inks from printers...while most are made with non-toxic chemicals, these do not fall under the law and may be bad for mice, especially those printers that also use the ink to print photographs.
However, you may also use phone-book paper, or plain note-book/printer paper, construction paper is good too, and can add that bit of color to a tank!
Personally, I use shredded newspaper and toilet paper. If you don't mind that the ink can sometimes make those mice who have light-colored coats look a little dingy, I far prefer it to straight paper. Newspaper is very soft in comparison...but I do want to warn you, besides making light-colored mice dingy, it also highly absorbent, so it's gets dirty fast, and thus can stink if you aren't careful. That's why I like to fluff it up with Toilet paper. Some people I know use a mix of newspaper and Carefresh, so on and so forth. Also...watch your shredder. Newspaper, because it's so thin and soft can gum up a shredder in no time.