Aquatic Life T5 HO Lamps are filled with a gas containing low pressure mercury vapor, argon, xenon, neon, or krypton. The pressure inside the lamp is around 0.31% of atmospheric pressure. The inner surface of the lamp is coated with a phosphor coating made of varying blends of metallic and rare-earth salts. The cathodes at each end of the lamp emit electrons when energy from the ballast is delivered to the lamp. This energy mixed with the phosphor transforms the ultraviolet radiation into visible light. The color of the light depends on the composition of phosphor. Each batch of Aquatic Life lamps is carefully tested to ensure consistent light output and quality.