This week’s Sunday Stills challenge theme is ‘Black or Metallic.’ See more responses here.

I’m going with the Black Triggerfish for this one. This fish is very black except for distinctive light blue lines at the base of the dorsal and anal fins. Even the eyes are black and very difficult to distinguish in the water or in photos.

The exception to this is when the fish is aroused. Then, blue lines radiate from around the eyes. The more agitated the fish is, the more color is displayed until the fish is entirely blue, yellow and green, except for the fins and tail outline.

These fish often gather in large numbers high in the water, feeding on plankton and drifting algae. But they also feed lower in the water, especially when sergeant fish eggs are on the menu.