Thanks for the compliment on my tank.
Sailfin blennies are cool little fish with plenty of personality.
The picture is sort of small to really tell what the coral is. I am thinking it might be some type of a finger leather based on the shape and coloration.
Most people don't worry about the coralline algae on the back glass, unless this is a peninsula tank. It is a sign of good levels and maturity. If it bothers you too much you can use one of those utility scraper razor blades and scrape it off. That is about the only thing that will take it off "easily".