Zoo Med UltraSun Daylight Compact Fluorescent Bulb, 10-Watt (3 Pack) 3 Ultra Sun mini compact fluorescent bulbs Each 10 watt bulb measures 5 inches long Emits 6500 Super Daylight that simulates natural daylight These small bulbs are excellent for use in Nano and small fish tanks Ideal for use in fresh water and reef tanks that need a high exposure fto natural light