Just to make sure that this gets said; you cannot leave the fish in the dark permanently. Fish need Vitamin D, and just like us, they make most of their necessary Vitamin D via stimulation from light. People get rickets if they don't get enough Vitamin D, I'd hate to even think of what rickets would be like for fish.
Sounds to me like you need some nice floating plants to break up the light. More regular plants -- buy some tall, medium, and some short ones, would be helpful too. Maybe a nice piece of bogwood, or some rock caves. There are lots of options that will provide the fish with the little nooks and crnanies the fish craves for hiding spots.
You have to remember you should be trying to replicate your own little slice of nature in your tank: lots of our aquarium fish come from streams and rivers, where trees usually grow pretty tall, so a lot of the time their waters would be in at least partial shade. So, there needs to be some light, but also there needs to be hiding places under roots, branches, plants, rocks, etc.
Fish will come out more often and become braver if they know that a good hiding place is only a few swishes of a tail away. If there are no good hiding places, they will become meek and stressed. The more hiding places you give them, more often than not, the more they will come out.
