I think a Royal Gramma would do fine. They tend to stick to the mid-upper part of the tank, well away from the bottom where your goby/shrimp pair live.
The only thing is, the gramma might hide in the rock work.
If you want something that is out all of the time, you might consider some type of clownfish (most of peaceful, though something like Tomato clowns can be aggressive). A Sixline wrasse is also a peaceful fish that is out-and-about during the day.