One of my friends has got a new vertical tank, (180x40x40) and he has it in his living room, where he has all the lights on all the time. (Why? He is weird)
What he did was created a U shaped cover out of thin wood (you can use cardboard or any other hard material) and painted it black. Now, when the fish want to rest, he just puts the board around the tank, which closes it down from the lights. It works great since it cant overheat equipment and doesn't let light trough!![]()