Mine only likes moderate flow. Try turning off you powerheads for a few hours to see if it makes an appearance.
Also, you might have a fish that is irritating it.
IMO coco worms are very hard to keep I have tried of and on with no great luck. I in fact have one in my tank that was doing great, now It has not shown itself for 3 day
What are ya puttin in the water to feed him with? Try squirting some phyto down in his tube. mine is in and out of his tube 24.7 just like my dusters do....
Danny
I have mine at the bottom front of my nano, he is out all the time. I also feed it phyto plankton when I feed the corals twice a week. I do turn the pumps off and use a dropper wait about 15-20 min before I re-start the pumps.