What are they like to care for? Requirements, difficulty level, whether you'd recommend them, particularly for someone who's not experienced with saltwater. Asking partly for myself and partly for a friend who's also interested, though my friend doesn't have as much experience as I do - but I can help him if they're not TOO hard to keep. I have some invert and coral experience.

I think sea cucumbers are mostly reef safe and mostly harmless to other inhabitants, although they can employ a defense mechanism where a substance similar to soap is released from their body. But I don't think this is usual. Some people swear by having some sea cucumbers in their tanks because I believe they eat algae and detritus? But I think they also need a large tank and a deep sand bed in order to survive and thrive. Otherwise, no care needed I would imagine. You just have to make sure the tank is appropriate for them.