Green Brittles can be a problem when the get big. I had one. I couldn't figure out where my small fish were disappearing to (i.e. a few gobies became missing). One night I shined a flshlight into my tank. I was very disappointed to see that the green brittle had captured my coral beauty angel and was in the process of killing it. Unfortunately, the coral beauty did not make it. I then captured the green hunter and took him to a LFS. I have heard of people that have had them with no problems, but I am not lucky enough to be one of them. Hope this true-life tale helps......