Christmas Tree Worm Rock (16+ month update)

I've had this colony of beautiful Christmas tree worms for 16+ months now. I don't think I've lost any more of the worms since I posted my last update (8 months ago). The gall crabs did sadly vanish about 3 months ago, the Cyphastrea has completely grown over the holes where they used to reside so you'd never know they were ever there. Three small bivalves have appeared where the tunicate used to reside, I assume they were hidden underneath the rock and behind the tunicate to begin with. They have gradually moved forward to keep abreast of the Cyphastrea but I fear it's only a question of time before they too become covered.
The worms have continued to extend the length of their tubes. I'd really like to know why this is happening, whenever I see photos of these in the wild the tubes appear short and compact and do not extend beyond the coral host much at all. Is it a flow thing, do they feel the need to grow out to capture more food or do they have to extend their tubes to keep from being overgrown by the Cyphastrea? If anyone has any idea please leave a comment below.

Видео Christmas Tree Worm Rock (16+ month update) канала Lisa Page