OK, next trick: Try putting a towel or cover around three sides of the tank.
Next: Instead of using your hood-light. Try shining light in through one of the sides.
Failing that, cut back on the brightness of the light. Floating plants are good for this, like Wisteria, duckweed, frogbit, Watersprite, even floating Anubias.
And/or use Indian Almond leaves, dried Oak leaves or Roibos tea to darken the water with tannins. This is good for the fish in many ways.
Just to reassure you, they eventually outgrow this pernicious habit.
Last edited by Hallyx; 09-21-2013 at 08:04 AM.