I can't really give you an answer for your question, but I've had a small frogspawn for about a month now and I don't think he's eaten any of the food I've given him. The same with my hammer. My torch, favites and platygyra all seem to be eating though.
Both the frogspawn and hammer will react to the food and start pulling it in, but when i check back about 30 minutes later most of it has been dropped by the tentacles. I'm using enriched mysid to feed with all the pumps off for about an hour. Now, that being said, both the frogspawn and hammer seem to be doing great. They're both open all the time, have great color and seem to be getting a bit larger.
I'm going to continue target feeding (i've got a great cleanup crew that picks all the leftovers off the sand and haven't seen any increase nitrates over the last month) in the off chance that they eat some of the smaller particles. I'm not worried too much about them not eating unless they start looking like they're declining in health.
