We have the two guinea pigs, Oreo and Fidget (he had too much energy to be a Buddha). I'm still working on upgrading their cage size, but I want a backup plan in case I totally mess up their cage. Anyways, their litter gets 100% changed twice a week. Within 24 hours of cleaning the cage, it's messy with poop. I can't stand the thought of the precious little piggies walking around in their own poop. Ariel kept his in certain areas so this wasn't an issue for him. Today, I put two litter boxes in the cage and I'm hoping to litter box train them. Not sure how it's going to work, but I guess we'll see. On a guinea pig forum, there were threads saying that cavys can be litter box trained. Wish me luck!