NE ideas? Hawaain Duster

Have you been target feeding them? Anything picking on one? My pair don't always come out at the same time, and a hermit crab used to sometimes try to hide in the cranny where one tube is--making that worm stay in, even though the other one came out.
 
Have you noticed any peices of the "feather" in the tank? It may have also popped its head and is re generating another one. They wont come out while they are doing this.
 
RIGHT

I've seen the smaller rock dusters do that. Interesting process. I'll bet that's what the duster's up to. You must see alot of those down there.

Anyone know why a duster pops it's top? Is it a molting process? Is it stress-related?
 
is there any change in current where you placed them... that could make one go back in too.
 
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