What's Going On Here...

[Dom]

I've been noticing that from time to time, some of my corals have these things coming out of them. Not all the time; the suddenly appear and just as suddenly, disappear. There is a pic below. Can someone please tell me what this is and why it happens?

 

[Retro Reefer]

Sweeper tentacles used as a defense against encroaching corals..

 

[mta_morrow]

I've been noticing that from time to time, some of my corals have these things coming out of them. Not all the time; the suddenly appear and just as suddenly, disappear. There is a pic below. Can someone please tell me what this is and why it happens?

They look like feeder / sweeper tentacles to me. A good sign of a healthy coral.

I have several euphylliia and a bubble coral that extend almost every time I feed my tank.

After a while the euphyllia retract their feeders. The bubble always seems to have its out, especially in the evening when the lights are ramping down