Clownfish Occasionally Sits Still On Rock

My clownfish in my 10 gallon nano FOWLR sometimes sits on the rocks motionless. It doesn't move it's fins, but I could see it's gills doing its thing. However, after a minute or so, my clownfish will instantly start swimming again, eating, and acting normally. It seems to only do this when I first wake out of bed or if I accidentally disturb my fish. It also does a similar thing at night, only it's on the left back corner of the tank and it only does it for a few seconds. It seems to have stopped doing this as of last month. I also did a major algae cleanup last week.

Do any of your clowns do this? Is my clownfish just being silly?

 

My clowns sort of float at the waterline in the back of the tank on their sides during the night, first night I had them turned on the lights in the morning, saw them and thought for sure I killed them but after 5 years, Ive accepted it's just how mine like to sleep aha they're very quirky little fish.

 

Mine do something similar. Someone explained to me that it's behavior common only in captive bred clowns. Apparently sleeping room is at a premium in breeder tanks, and each fish kinda learns "it's spot" and keeps the spot even once the crowding is gone. Not sure how much truth there is to it but that's what I was told and it makes sense.