I am definitely not an expert....but I did have a majano problem a little while back. The pic that you posted doesn't look anything like what I had in my tank. IDK if they come in different colorations though. If I were you, I would put them somewhere so they can be watched without having to worry about them taking over your display tank, so perhaps a separate small tank. Just for a little while. If they reproduce quickly, then get rid of them. My majano population doubled in about a month, as a reference. If they don't reproduce at that speed, then a small little anemone would be cool I think.