It works as its supposed to but....
1 - The little filter pad needs cleaning EVERY water change.
2 - The cables are a mess (1 for UV and 1 for pump)
3 - To replace the bulb means buying a whole sealed unit at almost the same cost as the UV
4 - Mine burnt out and stopped working after 4 months. I was running it 24/7 but that shouldn't be a problem.
If you have an external filter I would get either a second hand Vecton offebay or a new one (The new version is supposed to be really good) I bought a brand new Vecton UV200 The new version but there are the old UV8 and UV15 going for below £30 inc delivery.
So overall the f r f works, doesits job but aesthetically and maintenace wise is a pain in the a**e. And my experience tells me it is not very reliable in the long term.
andy