I know that blennies have the ability to change color under certain circumstances but I haven't heard of what happened to mine. I have had the little guy (about an inch long) for 4 days now. The first two he hid which is expected, or was just very hard to find in my 90g. What is odd is that he is now flying around the right side of my tank, perching on anything and not afraid of anything, including me. The thing is he turned from a brilliant golden color from when i got him to jet black. He has no markings, blemishes or otherwise on him. Is this common for such a drastic change in so little time?