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Sorry about your dog.

Bedding: The purpose of some sort of bedding material is to absorb urine and odors and to minimize your pets' contact with their own waste. Some people use fabric to cover the levels and/or floor of their cage. The benefits of this is it's reusable and there's less waste but fabric is crap at controlling odors so needs to be washed very regularly (every few days) and some rats destroy it pretty quickly. Loose substrates are generally better at absorbing urine and odors/ammonia but can be a little messier and create more waste. Personally, I use a combination of a loose substrate (aspen shavings) on the floor of the cage and fleece mats with an absorbent inner layer on the platforms of the cage.

There are lots of loose substrate bedding options but the main things you want to look for are good absorbency, good odor/ammonia control, as little dust as possible, fragrance free, and low cost. Nothing gets 10s across the board so sometimes it just takes some experimentation to figure out what works best for you, your rats, their cage, and your lifestyle. Some good options I've used include fragrance free paper pellet litter (bags made for cats are sometimes cheaper), "crumbled" paper litter, soft paper substrates like Carefresh or Clean & Cozy, and aspen or kiln-dried pine shaving. You can also just cover the floor with sheets of paper and they'll have a blast shredding it up and carrying it all over the cage. Blank newsprint is pretty cheap at the hardware store and you wouldn't have to worry about inks. Paper would get gross quickly and would need to be changed very often.

Food: The most widely available recommended pellet food is Oxbow. You can get it at PetSmart stores but it's cheaper on Amazon or Chewy. Oxbow is generally free fed (always available) but it's good to supplement it with fresh veggies and/or a little bit of a grain/seed mix every few days. Other recommended pellet options are Envigo Teklad (also available on Amazon - 2014 formula for adult rats and 2018 formula for juveniles) and Mazuri. For nutritional balance reasons, you might want to make sure that 70-80% of their diet is the pellet and 20-25% is supplemental. This equals out to only about 4 to 7 grams of supplemental stuff daily, per rat.

Cage Accessories: For the most part, you can fill the cage with literal garbage and your rats will be happy. You don't really need to spend any money to make a cage fun for your rats. I try my best to avoid purchasing overpriced pet-store items. You can use cardboard boxes from the recycle bin, ropes and small baskets and bins from the basement, thrift shop, or dollar store, scraps cut from old clothes strung up with paper clips as make-shift hammocks, etc. The hardware store is also a good place to find fun cage items. A cluttered cage is a good cage. I like to have as many hammocks and hides as I have rats so they can all have their own spaces if they want to be alone. It's good to have at least a couple sets of hammocks because they need to be washed frequently. I wash all fabric cage items 2 to 3 times a week. Cardboard and paper items get tossed weekly because they also start to smell awful.

While you don't need to spend any money on accessories, there are some things that are worth their weight in gold. Space Pods are wonderful. I drill a hole in the bottom of them so pee drains out. Lava ledges are good for keeping nails trim and when strategically placed, they can be used instead of those stupid ramps. I love bendy rope perches, they're great for creating "steps" to higher hammocks and stuff.