How stressful for corals to retract multiple times a day?

[jamal-188]

I've been noticing lately how annoying some of my shrimp are to my corals. They run across my alvepora/frogspawns/kenya tree coral causing them to retract several times a day. I"m assuming many others have this problem and it's not too big of a deal but does this really stress out the corals or do they just retract then extend with no problems?

 

[jackdp]

I wouldn't think its much cause for alarm. In my tank hermits and snails are always going over my sarcophyton, it closes up and as soon as they've passed it's polyps are back out again. I'm sure in the wild things crawl over the corals too. If something is physically damaging the coral then you've got a menace in your tank.