Box fish doing flips and barrel rolls? Sick or just playing?

[Lovemyocean]

My box fish was doing twist and turns today around my tank. I haven't caught him doing it before. I got a video of it but I don't know how to upload it.
He looks like he's playing. Do they do that? Or does he have some sort of indigestion issue?
I saw him poo, it was green. Probably from the seaweed I feed him?

It was pretty cute watching him swim around doing those tricks it looked like he was trying to do it. But I just want to make sure it's not something bad I haven't heard of before.

Any opinions?