How old is your U.V. bulb, they should be changed every 6 months.

U.V. helps me keep my Powder Blue tang Ich free. Each time I have taken the U.V. offline, the Powder Blue has had an outbreak. When I put the sterilizer back in service the ick problem resolves itself. This had happened about 6 times now.

You would think I would have learned my lesson by now, double check everything...