Aquatop 5W to 13W UV Replacement Bulb (Gen 2). The ultraviolet replacement lamp compatible with Aquatop’s second-generation UV sterilizers and filter units. This bulb emits germicidal UV-C light that helps eliminate free-floating algae, bacteria, and parasites in aquarium water. Replacing the UV lamp regularly ensures effective sterilization performance; the Gen2 design provides optimal fit and output, aiding in maintaining clear, healthy water for fish and aquatic plants.