Delta EA - Pondmaster 40 UV Light Bulb for Germicidal Water Treatment cf-size-1-gallon Base: G23 Coralife - Turbo

Base: G23 Coralife - Turbo Twist 9W UV Light Bulb is 9 watts and 100% compatible with germicidal OEM Water sterilization filters

This 72Watt bulb emits UV-C light of 254nm

the dichroic light reflectors help in reflecting the UV rays efficiently

this is most likely the culprit

Delta EA - Pondmaster 40 UV Light Bulb for Germicidal Water Treatment cf-size-1-gallon Base: G23 Coralife - TurboGuaranteed Replacement Ultraviolet (UV) Bulb 4 Pin on a Single End 41 Watts 33. 2 Inch Length Lamp Worry Free Performance for 1 Year Product Overview: Specifications: Compatible With: Wattage: 41 Watts Wavelength range: 254NM Length: 33. 2 inches (843. 3mm) Base: 4 pin on a single end Base Material: Ceramic Bulb Shape: T5 Average Lifespan: Up to 10,000 hours Delta EA Pondmaster 40 UV Light Bulb is 41 watts and 100% compatible with germicidal OEM Water