#uv

So I’m in an interesting situation, I have access to a 18watt UV sterilizer my problem is my total water volume on my tank is 140gal. The UV sterlizer is recommended for 100gal I know the answer is odvious but can I use it on my system?

I just need some help figuring this out, on brs I see that some UV sterlizers are 25w but 450$ while others are 25$ but for 250$.I’ve read through them and see no differences so I just need someone to tell me their oppions in what I should do