Wow, this thread was ultra convenient. I just fed my torches like half an hour ago and always get the same sort of response, shrinking up, sliming, and deflating. I have found that they tend to eat more when the lights are lower intensity. I've been upping my lights to improve coloration, but the feeding response is no longer the same.
I think I may just axe the feeding thing with my euphyllia. I have to play goalie and block the incoming shrimps and fish and they don't wolf it down, so I'm not sure it's worth the trouble, unless it really does improve coloration.