Can anyone ID this wierd stuff?

[Arsenix2001]

This has been slowly but progressively spreading out from underneath an purple gorgonian frag I put in last November. Its clearish white and is forming almost like tube structures.

 

[Highgrade]

Sponge

 

[Copingwithpods]

It's a sponge of some kind (also some aptasias) 99% of the time they are fine but every now and then they grow aggressively and can smother corals.

 

[Arsenix2001]

Thank you and yes noticed the aptasia. Have a hand full in the tank and have been battling with lemon juice and syringe. 50/50 luck so far.