I'll disagree with the 'nems don't need food' statement.
I have rockflower nems that have come from shallow water (less than 3') in the Keys. They are kind of 'plain Jane' looking due to colors being tan, off white, gray, light green and such. But they did get a lot of light and they have proven to me that they don't need any intentional feeding.
On the other hand I have a number of rockflower nems that have come from deeper water (40' deep) in the Keys. These nems are crazy cool fluorescent colors that look spectacular. But they came from deeper water (and therefore less light) and don't seem to do very well unless they are fed. I lost a couple and the rest (I have about 20) were getting smaller and smaller. They never lost their vibrant color, but several did 'disappear'. This was over a period of about a year and the tank was well fed, but I didn't specifically target feed the nems.
But once I started target feeding them, they all responded. Over the last 6 months they have all stopped shrinking and some have actually started to get bigger. They were mostly 1" to 2" and several of them are now 3" to 4". This is in a tank system that is several years old and has mostly sps and lps coral where very little else changed.
So my conclusion, and I admit it's not very scientific, is that nems from deeper water that don't get as much light do better if they get some target feeding.