You know, it's funny, one of these posts leads into another, and here we go again. I got thinking about the hermit crabs (thought about blogging again last night, since it wasn't until after Tim toddled off that I finished cleaning their tank)...maybe it's okay that they stay in his room and turn rank...that is, other than their smelly effect that would augment that which an 8-year-old produces all on his own...
That is to say, I don't think hermit crabs care if their tank gets filthy. I have three pretty good pieces of evidence and one minor piece. The first is that I know that crabs are bottom feeders, that is, scavengers, who eat what other animals leave behind as inedible. Also, one of the first things Tim's crabs will seek out when left out of their cage to walk on the floor is any shoe of Tim's. Even when all of ours are lined up against the side of the stairs, they invariably choose his. They love his shoes, whereas often these shoes get so bad by human standards that we throw them out, since at times, no amount of cleaning them cures the problem--you can smell them across a football field lengthwise. Yes, they love his shoes, and the surliest crab loves our laundry room. Maybe it's the smell of Tim's socks that draws him. But one time he disappeared and I found him about two days later in the dirty clothes. The next time, he disappeared and I found him about two weeks later, alive, in the dirty clothes. (Yes, I had been doing the laundry consistently all that time. I think he hid behind the dryer.)
The last evidence is that once you clean their cages, they just kind of look lost in the new, clean sand that goes in. They just look kind of confused and like they're trying to get their bearings. I think it takes them a couple of weeks to start getting happy. That is, if indeed those are smiles on their faces. It's kind of hard to be sure with hermit crabs.
All this analysis of their behavior shows me that you can't kill them (one day in the dirty clothes would certainly kill me), and that beauty is definitely in the...what are they on crabs...nostrils?...of the beholder.