cage clean up

Hi everyone! Long time no talk. Pepper developed kidney disease symptoms around age 5 but in the last couple of years (he's 10 now) he developed kidney disease. He is on medication and we just saw the vet for a blood panel over the weekend. His kidneys looked rough four months ago but after...

So my Jenday has developed the skill of pooping outside of his cage when he's in the cage.... My carpet does not appreciate this and I'm sure my landlord will appreciate it less. Any recommendations of something to go under his cage> I've considered an office chair mat but am open for any ideas!