bohlke,
That depends on what kind of benifit you are looking for. If you are looking for something that rapidly uses up available nutrients, I don't believe they would be of much benifit. If you are looking for an interesting marine organism to add diveristy to your tank, I think it would be of great benifit. I have not know members of the two genera I listed to be particularly rapid grows or to cause harm to tank mates. So assuming it is in one of those two genera, I would lay odds that keeping it around would not be a detriment to your tank.
Jay