could very well be the case then. as mine never closes at all as far as I
can see, he/she is always open and "arching" away. I have quite a few
hermits and such but they leave it alone.

as for your sand getting in it, how old is your tank? sand will get a
bacteria coating over it and be more stable as time passes and wont be as
easy to "upset".

or do you have something stirring it up?

kc