Not the cleanest things but I drew some thumbnails today to get an idea for the narrative. As a bright and colourful world it might be best for the characters themselves to be just as expressive. They can be colourful, but also being expressive would be very useful.
It's not just the colours or the fish though, patterns could also be useful to portray the world. And even if we kept these minimal there are the patterns like the circles blowfish make to attract mates. Patterms could therefore be an important factor in the creation of the world.