Basic question on sps polyup extension

[TbyZ]

Forgive my ignorance in all things sps.

Should a healthy sps exhibit polyup extension to some degree throughout the illumination period or just after feeding for a limited period?

 

[mpsteve]

Most all of my acros show polyps 24/7 some show a little less during the day but there still there

 

[Mattrg02]

Only one of my acroporas, a Walt Disney frag, show any decent PE. They'll start out with plenty of it, then barely show at all. So far, they seem to be growing.

 

[Salty1962]

Most corals have their PE during the dark photoperiod. They do this in the wild to gather the most plankton and keep predators from eating them. Look at you tank at night and you'll see another world in it.