Cover the light fixture with aluminum foil. Cut small slits it it to let some light through, start with small holes for less light. Little by little increase the size of the holes as your p's get accustomed to it. That what I did and now my p's are hardly ever skittish. to move them with the gravel cleaner when doing my water changes cause they think they all tough now. hehe But that what I love bout them! Good Luck!