Do all fish sleep?

[ScubaSkeets]

My tank lights are full off from 7PM to 9AM with an hour ramp up/down.
I have a weird sleeping pattern so I wake up at various times and I'll take a peek into the aquarium. Sometimes midnight, sometimes 130AM, 3AM, 5AM, etc...just different times throughout the night. I'll make sure not to startle the fish and the only light is the ambient light from the LEDs.
And no matter what time I check, my Heniochus Butterfly is swimming around! The Tangs, Anthias', Clowns, Wrasse, Blue Spotted Puffer, etc, are hiding/sleeping, but not the Heniochus! He NEVER seems to be sleeping!
Is it possible that he just doesn't sleep?

 

[littlefoxx]

My tank lights are full off from 7PM to 9AM with an hour ramp up/down.
I have a weird sleeping pattern so I wake up at various times and I'll take a peek into the aquarium. Sometimes midnight, sometimes 130AM, 3AM, 5AM, etc...just different times throughout the night. I'll make sure not to startle the fish and the only light is the ambient light from the LEDs.
And no matter what time I check, my Heniochus Butterfly is swimming around! The Tangs, Anthias', Clowns, Wrasse, Blue Spotted Puffer, etc, are hiding/sleeping, but not the Heniochus! He NEVER seems to be sleeping!
Is it possible that he just doesn't sleep?

He probably sleeps lol just now when you look in! My purple tang was like that too. She never looked like she slept. My naso tang now is always swimming around like that too lol but they have to sleep

 

[Goaway]

Some fish sleep half awake.
unihempispheric sleep is an interesting read.

 

[Gumbies R Us]

My clown will sometimes look dead in the corner of my tank. Nope, he is just sleeping.

 

[Uncle99]

Mine does the same. Always cruising.