If you want, you can dose DT's or other prepared phytoplankton (Kent's phyto or microvert) once in a while for your feather dusters, etc.
For the corals, just feed your tank (I assume you've got fish). Some of the stuff that falls down will land on the corals, and feed it. I alternate a variety of frozen (brine, formula 1, etc.) and dried (flake, pellets). If you want to be obsessive, use a turkey baster to target feed the corals, but I don't think you need to.
Very comical to see a coral maybe pencil eraser size try to swallow a chunk of frozen-defrosted formula 1!
I have a tang, and put in Nori once a day. The tang has horrible table manners, and shreds the Nori while eating it, so there's pieces of Nori floating around. The snails, hermits, porcelain and red emerald crabs love the Nori when it gets within claw range.