Still not sure I'm getting it but I want to clarify a point. It won't "blow" in the dark. It happens at first light or shortly thereafter. When I see it before I go to bed, I know I have until the next morning before the lights come on to get it out.
EDIT: And just to add to that, if your tank is in a room with lots of natural light "first light" can also mean the natural sun, not just the tank's light.