What is this red thing on my coral? Red sweeper tentacle?

[pharmr]

Hi. I’m new to this hobby- 6 months in. 75 gallon, zetlight ufos, reef octopus hob skimmer - fx4 canister Fish and corals tank doing well and growing But about a month after I got this coral (hydnophra???) it got a red spot on top With in another month the spot extended to this thread like thing It retracts sometimes. Is this a sweeper tentacle? Never seen a red one. Online they all appear to be translucent. Anyone have any ideas?

 

[blaxsun]

No. Mine are all white/translucent on my hydnophora. Is it a hitchhiker?