We've been amused for weeks with one of my kubotai. I was cleaning my tanks and stacked two coconut shells halves on top of each other to make room for vacuuming. Somehow, I didn't put the shells back where I found them, and we soon noticed that one of the kubotai had taken up residence in the top half. He guards it fiercely. Here is a picture of him making sure that no one is getting too close.

Now, my kids want me to add a third story to see what happens.
