The green brittlestar is a known predator in the wild, however, not everyone has this experience in captivity. Some do, some don't. Even some who feed them, still have problems. Mine is not. In fact, I have a dead snail in that tank right now, and he (and a serpent) are sitting there next to it looking forlorn, wondering how to eat the yummy smelly thing.
Some people report the green eating anything...shrimp, crabs, snails, fish.
Mine is very large (and grew very fast, BTW), but appears to be pretty docile.
There is no biological distinction between brittlestars and serpentstars, and my serpentstars are rather aggressive feeders. Some of my brittlestars are rarely seen. Others report the same species of brittlestar hunting. I suspect it is an individual thing, and no one can guarantee how your brittle will behave. It may eat something, it may not. It is a great risk to small fish- damsels, clowns, gobies, etc.
Keep any brittlestar or serpentstar fed...do not allow them simply to scavenge. This may simply mean putting a piece of food near it, or into its arms, or something. They will eat just about anything, but we tend to load our tanks full of scavengers. Just good to make sure it gets something.
Yours will grow big, fast. But they are good in a sump or refugium should you have any problems with it down the road.
