blue tang ???

[larrynews]

any ideas to why my blue tang has started banging his head up against the glass only one the one section bottom left corner , and before i get all the obvious answers not ick or stray current, at first i thought that maybe it was seeing its reflection  and was going after it,its about 6-7 inches i have it for a while close to a year if not a year, very one else is fine and he only acts like that every now and then
thanks

[REDPYRO]

frustration of being in a tank...

[larrynews]

ya know i thought about that, i have read about tangs in 4 ft tanks, but was hoping it is something else

[REDPYRO]

probably out grown the swimming area