Uv - Before Or After The Filter?

[rjsmith]

Hi,
As the title suggests. I've bought a second hand UV for my tank and wondered if it makes any difference where I put it in the pipework - before or after the external filter?
Cheers.

 

[olly24]

i was always told after

 

[The-Wolf]

after makes more sense as then you are only steralising clean water.
before means you are trying to get uv light through all the impurities etc and the muck could accumilate on the quartz sleeve.

 

[rjsmith]

Yep, that makes more sense. Should have figured it myself.
Thank-you.