Hi All,
There is a small group of avid night flukers that I know that have tremendous success, especially with large fluke.
As a SCUBA diver, I will tell you they there and do feed. I believe like most ambush feeders, when an opportunity presents itself, they take advantage of it.
Like Far26 said, it is my personal opinion that they hold closer to hard structure.
I do feel that the animal world has a sense of "night" and actually "sleep." One great example are Parrotfish. However, there are hungry critters down there, maybe not as active or as many.
Just a few thoughts,
Capt. Ed