i use a Canon 60D with 16-35mm lens f2.8 and canon 580EX flash. from my experience it is better to take pictures at night or in a dark room. in tht case, less sunlight will come through the tank and pictures will not be too expose by the light and much more sharp. i usually dim out the lights and depends everything on my flash. from all of tht, i edited my pictures using Adobe Photoshop CS6, but while editing, dont make the fish's colours too bright, tht will only fake it.
