Originally Posted by ReefStar
ok, i found a site that comapred serpants with brittle stars and i think there black brittle stars, so are those good to have?
There is NO comparison whatsoever as they are the same animals. Anyone who says otherwise, and makes behavioral distinctions in particular, is wrong. This is a distinction made in the hobby only, based on arm spines, and has no biological significance.
Unless you have Florida LR, where you may get larger species as hitch hikers, you almost certainly have mini-brittlestars. These are very common hitch hikers, probably an Ophiactis or Ophiocomella, and will not get larger. They are fine to have, and will likely reproduce.
There are probably dozens of species that could be called "black brittlestars" and I would not trust 99% of any hobbyist site trying to identify them.