I'm running a couple of biocubes: 14 & 29 gallon. Here are my recommendations for a peaceful tank.
1) I recently became a big fan of having a single flasher wrasse in each. They are not aggressive but will extend their fins and "flash" to other fish e.g. clowns, firefish etc. They add colour and beauty.
2) For gobies, I like the high fin black ray gobies and the other shrimp gobies paired with a colourful randall's shrimp (tiger striped get too big for the high fins). Neon gobies are also interesting but they will pull food out of the mouths of the corals even though their bellies are already full to bursting!
3) Firefish are always good but can be secretive; only coming out when food is present.
4) If you can provide the necessary food, dragonets are amazing in their swimming abilities; hovering vertically or upside down as they peck at the live rock.
