IMO, it really doesn't matter as long as you don't get the green brittle or serpent. These are known piscivores. Otherwise, get whichever one tickles your fancy. Personally, I find serpents are less cryptic than brittles (ie, don't hide as much).
One of my tanks had a grey/white striped brittle and a large red serpent. I see the serpent all the time, but rarely saw the brittle. About a year ago, the brittle disappeared. I figured it had finally died behind the rocks. Two weeks ago, I was doing some work around the rear, built in wet/dry filter area (I have a SeaClear System II, and I've turned this area into a refugium area). As I was looking down into the triangular overflow area, I saw one of the brittle's arms sticking out on the bottom from the next chamber. The next chamber is the skimmer chamber. So I guess my brittle is still alive and well and living next to the Rio 600 in the skimmer chamber. Now that's cryptic!
Kevin
[ February 28, 2002: Message edited by: Anemone ]</p>
feed him well. i feed my green brittle a large piece of fish or shrimp( size of a quarter) two or three times a week. he has never bothered anything in my reef. i think they all can be different as far as diet goes.
Ophiuroid posts very knowledgeably on brittlestars and maintains a great website about them http://home.att.net/~ophiuroid She has pointed out that there is no biological difference between brittle or serpent stars, but that the distinction is made in the aquarium trade only. She has advised to be cautious with the green "serpent" brittlestar Ophiarachna incrassata which even if spot fed may yet eat other tank inhabitants.
Roy- thanks for the plug! I think that most brittle/serpents are fine, but some folks have reported trouble with the green guy (can't remember if it is considered a brittle or serpent, but it is the most common form I have seen!). I would suspect, however, that the number of people who have had trouble with them versus the number of people who have them is pretty low. For the most part, I reckon they stay out of trouble. Still, anything is a possibility. I would say that all brittles/serpents should be kept well fed by spot feeding with meaty bits (shrimp, squid, fish, shrimp pellets, etc). Do not leave them to scavenge! If they decide to eat anything, please remember they did it because they were hungry, not because they were bored and wanted to tick you off.