34-Inch Fluval Sea Actinic T5 Aquarium Fluorescent Bulb, 39-watt. Provides strong and essential actinic blue spectral peaks Strongly recommended for photosynthetic coral, invertebrates and other marine life Visible dominant blue spectrum highlights blue coloration in fish, corals and other invertebrates Longer life versus other comparable high output fluorescents Maintains superior light output over the entire bulb life versus other comparable fluorescents