How's the water out here (Surrey)?

[Doormatt]

Hey all you locals

I'll be starting up my 37G reef soon, and wondering if RO/DI is totally necessary. They're not exactly cheap, but at the same time I don't want to ruin my chances for success, just because I skimped on one thing. I'm in surrey (Scott and 80th area), and just wondering if other surrey reefers use RO/DI.

Thanks!