This is the first of a series of shots from the Ripley's Aquarium in Gatlinburg. Getting good images in an aquarium, especially a crowded one, can be very challening. The lighting is poor, the glass tanks are reflective and typically covered with fingerprints, and the fish are usually moving rapidly. Not very conducive conditions, necessitating wide apertures, high ISO settings, to allow shutter speeds sufficient to freeze the action.
This shot was taken with the Canon 50 mm/f1.4 lens at ISO 800, f/1.8 at 1/60 second.