Do you have any new fish or a fish that might be picking at it? When mine goes like that some fish is nipping at it.

Dave

Man as soon as the lights go out in my tank, my brain opens right up and out come all the feeder tentacles, they are out till around 4am (yes i have watched this one drunkin stuper)

Personaly, my open brain is my most favorite piece in the tank, that and my frogspawn