What are these tentacles coming from my live rock?

[johnf3]

I recently added some ocean aquacultured live rock to my tanks that came with all sorts of cool sponges tunicates etc. Added a really nice piece to my macro tank. I’ve noticed a few bristle worms crawling around when the lights go out which I don’t mind. I was checking for other critters last night and noticed these strange tentacles coming from the rock in varying lengths/widths making a jerky motion. They were extended a good 4-6 inches out of the rock before I shined the light then they suddenly all jerked back towards the rock. I took a vid, link below. Any idea what this could be? Seems to all be branching from one critter but not sure? Please lmk if you have any ideas! I’m excited about whatever it is.



Thanks

 

[Crabs McJones]

Digitate Hydroids

 

[johnf3]

Digitate Hydroids

Ah yep. I have only dealt with the tiny hydroids on glass before so this is a new one for me. The tank is just macros so they should be fine right? I can possibly try starving the tank since it is only macros and snails

 

[Crabs McJones]

Ah yep. I have only dealt with the tiny hydroids on glass before so this is a new one for me. The tank is just macros so they should be fine right? I can possibly try starving the tank since it is only macros and snails

I had them in my tank, never really caused an issue. overfeeding will definitely bloom their population. If you just have a couple I wouldn't be too worried