Were they eating when you got them? i find anthius do well in our tanks if they are fed often. Not big feeds but more of little but often. I have 28 anthius in my tank
7 sqampinnis (lyretails)
21 kashiwea's all take, brine, mysis, flake, and pellet food out of my Eheim auto feeder. The pellet food is ocean nutrition. As to getting them to feed, just be patient, and feed small amounts of frozen brine first. Normally when one fish start, they go into a feeding frenzy. Good luck hope it goes well for you...GT
You can often get them started feeding in aquariums by giving them small live feeder guppies. They should go crazy for these. Live brine shrimp is also very tempting. Don't dilly-dally around trying to find something non-living that they will take right away. Hurry up and get them the live food as these fish can't go without eating for very long! Once you get their bellies full then wean them to frozen or dried.
as was already mentioned, i'd try some live brine shrimp, etc. to get them feeding now... they won't last a couple days without food. when you get them to eat, they need to eat 2-3 times a day. once they are eating, i've had good luck with the frozen mysis shrimp that premium sells. let some of these blow out of a powerhead, etc. (to simulate live food) and they will usually gobble them right up. hope that helps.