I love the Dragon Goby for cleaning the sand, also known as the bullethead goby. Constantly sifting the sand. Substrate has never been cleaner. I have a peaceful tank, so not sure this is what you are looking for. My is about 2 1/2 inches and still does a great job in my 75 gl. My LFS has the Dragon Gobies in all sizes though.
Have been told by an expert that dragon gobies live longer because of some good bacteria they house. FYI.
Good luck.