there's also one obvious reason why some of our fishes stay at the bottom at times...their tummies are full! these fishes have huge appetites and they need the quiet rest in a corner for digestion. i've also read somewhere that being an ancient species, they're not equipped with modern fish swim bladders, hence the prefer swimming most of the time even when sleeping.
ofcourse my aquarium lights are regulated on schedule but what i'm really interested about is the question on artificial lighting effect on growth. i mean, all of us want to show our fishes off right? just wonderring if there are health consequences at times