I've been wondering about this for a while, will there be much a difference with regards to yield etc? Or is red the only way to go? I know red is supposed to be used but.....money, money money!

Yes a blue spectrum can be used for 12/12. Of course a higher red spectrum is better for flowering but not neccessary. You don't have to spend a lot of money though, HPS aren't the only way to get an increase in red spectrum, you can find flo's for cheap that have any spectrum consentartion you want. I got a 9ft settup and 2 lights for only $30.

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Nice one, cheers

where did you get the Red flo's?