Odd looking tentacle appendages coming out of your live rock could be a basket starfish or a cucumber! Basket Starfishes like to hang out on the sponges and under our live rock. We see some amazing ones and always let them be.
Our goal is not to collect basket starfish as delicate, so alert professionals via social media to help. In the event one makes its way into your tank they will extend their net of tentacles sifting phytoplankton from the water column.