I read this thread a few days ago, and had a good chuckle over some of the replies.
Yesturday I brought Chernobyl home and he had a great day exploring his tank. All good there.
This morning I fed him, told him to be a good boy, and took off for work.
When I got home, I looked in his tank; no Chernobyl. Panicky, I looked on the surface, no Chernobyl. Finally I found him hanging out on a plant being all cool.
Later on, I looked back in the tank, and this time he really was floating, just under the surface in a C shape. I almost freaked out. Left the room for a minute, and he was back in his corner waiting for food!
I think this was payback for scaring him this morning, so much that he nearly flew out of his tank. Poor baby.