Polyp Extension on only one side of acro

[SaltyRaggae]

I recently added my first round of acro frags in the new larger tank. I have good PE on tricolor valida/nana/random acro frags, but I've noticed on my green slimer and red millepora that I only have polyp extension on one side of the frag.

The polyps will extend on the side where the flow is blasting them, but not on the leeward, protected side of the frag. The side without polyp extension is also facing down. Is this normal? will the polyps eventually disappear on the underside of the frag? on the "healthy" side i can even see mesenterial filaments being extended during feedings, but nothing on the side not being blasted.

My tank is a peninsula, so I have no flow coming from one side, just a strong, noticeable undertow. Is this an issue?

 

[Eastone]

some sps will have a lower polyp density on the lower branches, and these polyps won't open as much, I see it most often on milleporas. It's nothing to be worried about if the coral looks healthy and there isn't any signs of recession or bleaching