Can nudibranchs be kept in aquariums?

Many types of sea slugs can be kept in aquariums, but nudibranchs are not one of them.  While many people try, they are not easy to keep and often end up wasting away over a period of months due to the fact that they are carnivores and that many of them have a very specific diet and even those whose diet is more varied still feed on animals found in a reef environment.