We have been using UV sterilizers here for years – 
they can be great and also worthless. The thing to remember with them is size and flow. The little ones sold in pet stores are almost worthless for the light needs low flow and large amounts of contact time. Either way you look at them they also have the added issue that they kill good and bad algae, hence we DON’T recommend them in the general tank.
As you can see by the video we recommend them in the QT system and they work great there if you get a large enough one. We bought this one years ago via Bulk Reef Supply and it works great on the 20 gallon QT.
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