I just found a huge nudibranch in my reef .It`s about 3 inches long and 2 inches wide solid black looks like velvet with frills . Its pretty cool looking .I put 2 in my tank 3 years ago but they had thin blue lines on them and they were real small I`ve changed tanks since then and Ihavent added anything . could it be one of those? Anyways nice suprise. The kind I like