i have a large duster that i have had for 2 weeks now..itused to stay open virtually all the time now it closes quite a bit...and the top of his tube has slightly caved in...he attached himself to the bottom of one of my base rocks...i think that im gonna start feeding some filter feeder food like phytoplex or something like that...what do u all recomment...look at my signature for my set up and life...i only feed the tank very little everyother day and think my duster isnt getting enough food