Light can indeed cause stress in new fish as they adjust to their environment. The intensity and duration of light exposure are key factors that can impact a fish's stress levels. Sudden exposure to bright lights or prolonged exposure to intense lighting can be overwhelming for fish, leading to stress-related issues. It is crucial to provide a gradual acclimation to light levels to minimize stress. Additionally, dimming the lights during the nighttime hours can help simulate their natural habitat and promote a more peaceful environment. By taking these measures, you can create a suitable lighting environment that minimizes stress and enhances the well-being of your new fish.