Why do clowns bob?

[Moort82]

Is there a reason why some clown species bob up and down in the water column? It seems more evident in younger clowns at least that i have witnessed. There is a young pair of saddlebacks which i've seen that have done this for the last year or so and i picked up a pair of nigripes today and they are still small but constantly behaving the same. I haven't seen this in my baby percs or adult perc/occs and the pair of pink skunks also doesn't.
I'm aware they aren't the best swimmers for obvious reasons but wondering if there was a reason why they do it.

 

[Moort82]

Any ideas?

 

[ClayaLaLeona]

Maybe is for protection when they are young? It seems a bit distracting when you have a swarm of bobbing clowns, just my opinion though.

 

[Moort82]

I like the idea and i guess distraction in a likely reason but i do know clowns don't swarm in the wild and that their shoaling behaviour when young is an intank phenomenon. Naturally they would settle out of the plankton more or less on their own.
I have seen this with other species as well such as bangaii's and wondered if the bobbing attracted food?