Weird Worm Thing?

[Eb0la11]

Hey guys,

so for the past two months or so I've taken note of this creature in my tank that is unfamiliar to me.

Its hard to explain but basically a tube has slowly been growing in my tank off of a rock. Its probably 2 inches in length at least on the exterior of the rock and who knows how much deeper into the rock. Its now half covered in coralline algae though. Within this tube, which has the diameter of the smiley faces when I post, so about this big , is a worm of some sort.

It barely sticks out, if at all. It has two antennae and out of its mouth it creates a type of web almost. Sometimes it will shoot almost like one strand across to another rock and other times there'll be a lot of this web swaying in the wind just below, as if it didnt attach across the way.

Im not sure if its using the web to filter feed or what, but its a weird creature and its tube grows a mm every week probably.

Anyone encounter anything like this and knows what it is?