especially lmb are structurally oriented. They must have something to "relate" to even if is the bottom.It does not have to be a canopy with a bunch of limbs. Just "something". An experiment was done years ago where a large square aquarium was built and completely painted white and nothing in it but a single 25 cent coin sitting in the middle on the bottom. I believe it was a dozen bass that was introduced into the white box. They wandered around awhile and soon EVERY ONE OF THEM positioned themselves over and around that single quarter!! They WILL use whatever cover they can find.

Dear Alcohol, We had a deal where you would make me funnier, smarter, and a better dancer... I saw the video... We need to talk.