[Surferminn]

Originally posted by Jim Sachs:

Though they dont have eyes, they are light-sensitive. The smaller ones like these are easily triggered by passing your hand over the tank, causing a slight shadow to fall across them. When the shadow has passed, they immediately open back up. I've slowed mine down to about half-speed in an attempt to avoid the "surely they don't move that fast" comments. I see that I was unsuccessful in this  

lol...One of my first thoughts was, "Surely they don't move that slow..." I have seen only 1-2 live clams and they snapped shut really fast like a reflex so I was kinda puzzled by these slowly closing. Then thought I might look around and do some homework before I put my foot in my mouth. And then after seeing Cliff's links, figured, well, maybe some of them do close that slow and let it go. Thanks for your comment above so I know I wasn't losing it. I'll just clam up now and admire your work.

Regarding the fishes, I have to say as I watched, sometimes I could swear they should be closing but they just sit there so I figure the fish must be closer to the glass than it looks. The best close connection I've seen is when the fishes seem to be foraging the pebbles nearby looking for something and then they close.