Extenral Filter & UV

[simonc5555]

Hi all

Currently have a 200l tank
2 wave makers
Protein skimmer
Live rock
Live sand
Cuc
And some fish

I'm looking on adding some tangs to the Fish blue tang and yellow tang but have been told it's best to add a uv sterilizer for them is it a better to get one that goes into the tank or one the connects to the filter ? I have an external filter but not sure what media I need to put in it can anyone advice me on

Uv filter
and media for external filter

Thanks