Frogspawn coral issues

[Vigor7]

I've got two types of frogspawn coral going on - one's purple, the other's green-tipped. Every day around 8 pm, the purple one shrinks up and the green one pretty much disappears into its skeleton. They're out for an hour, then they're back to normal. Lights are still on, no changes there - 11 hours a day, 12:30-11:30.

They look perfect before this happens, so I'm stumped. Anyone have a clue what's going on? All my other corals are thriving, anemone's doing great too.

[SparrowFly]

I've noticed that my LPS corals change throughout the day, they can look nice and plump one minute and then be deflated the next. It's like they're going through some sort of daily cycle. I've seen anemones do the same thing, and to be honest I'm not entirely sure why it happens. As long as they're growing and looking healthy overall, I wouldn't worry too much about it.

[beachcomer]

Mine have done the same thing since I got them, almost 9 months ago now. Same time frame too, around 7-8pm. My frogspawn went from just two heads to a full nine, so I stopped worrying about it.

[floralix]

They are filtering for food when they're plump and inflated. Then they retract to expel waste, basically pooping.