Bacteria bloom with UV

[coronarex]

I am experiencing a bacterial bloom in an almost 2-year-old bare bottom tank. The tank is 100 gallons with a 25-watt UV running 24/7. I have experienced this once before, about 6 months ago (It cleared the next day). I have 2 Bangia Cardinals, 2 firefish, a carpenter wrasse, and a Yellow tang. All have been in the tank for a year. Any thoughts as to why this is occurring? Thanks

 

[blaxsun]

When was the last time you checked your UV bulb and cleaned your UV?

 

[coronarex]

3 weeks ago. bloom is gone now, lasted about 12 hours. i also noticed a few brittle stars floating around in the tank dead

 

[SteveMM62Reef]

Any Chemicals used in the house, that aren’t normally used? IE something used to clean with before the holiday? I have to replace my UV Lamp once a year, I can always tell when it’s failing by looking at the Growth inside the Semi-Clear UV Discharge hose. Or by seeing a slight Greenish tint, when I do a water change, in the white buckets.