Technically they are a "sea slug" not a "nudibranch" but don't ask me what the details are that separate the two groups.
Supposedly they will adopt some photosynthetic abilities from the chlorophyll in the algae they ingest.
A few years back I tried some on two separate occasions. Unfortunately, in both cases, they withered away over a few months and eventually disappeared. I don't know how typical of a story this is, but I haven't tried any more since then.
They're really quite pretty, ornate, creatures. I might try again some day if I can learn some more about them beforehand. I guess they have a relatively short lifespan but it's possible to breed them (if I understand correctly what I'm reading about them).
Sorry I can't be a better help..
PS. There is a seaslug forum which may have more information, specific to nudibranchs and seaslugs:
www.seaslugforum.net .. Also Calfo's "Reef Invertebrates" has a chapter on them. The book looks great, although I only received my copy a couple days ago and I haven't actually read that specific chapter yet.
PPS. Here's a starting point for further reading:
http://www.seaslugforum.net/factsheet.cfm?base=elyscris