I was using a 60 watt red light bulb, which would almost run at full wattage to keep the tank heated. I noticed it was pretty bright, and seen less of my bp at night. I switched to a 75 watt on thermostat, and that seems to run the bulb 50% dimmer at day/night. Much darker tank at night, and he's back to being out a little more at night around feeding day.