Get a blenny. Just be sure to have enough algea and such, old/good/been in there a while live rock.. I prefer the Zebra Blenny, also known as the Hawaiian Algea Blenny. They are usually gray, but at night, and sometimes when together, they get they go through an amazing color change. They get off white stripes all over them. Sometimes they are covered in them, sometimes only a few of the stripes show up. They also become very friendly very fast. Today, I got my Zebra Blenny to suck on my finger six or seven times. He also comes right up to the glass when you come up to the tank. I would also recomend getting two or three of them, seeing as how you have the possibilty of getting a male and a female. Also, if their gills get white all of the sudden, don't worry, they're fine. They only seem to do this when around one of their species. I suspect that when they get their stripes, they're trying to attract the female. Then again, I could be completely wrong.