In one of my prior tanks, I had brought in a random rock that was covered in Christmas tree feather dusters, but its was not a Spirobranchus porites. It could have been I suppose but only if the coral portion had died. I was told these micro feather dusters would not spread through the tank. For a while I thought this to be true however, after a few months, my tank was filled with these micro feather dusters, various colors, red, black, orange, yellow, pink, blue, basically every color of the rainbow. They even came in multi color versions however only a few of these. Well I am doing all that I can to recreate this and as such, have added a Spirobranchus porites to my tank to hopefully allow it to spread among the tank. I have also added a few large feather dusters for the time being, and researching ways to propagate these tiny coco worms.