When should I change from MH to HPS?

[Dutch Pimp]

Hi Guys,

Just a quickie. I'm now in my 12th day from changing to 12/12 and was wondering when to change over to my 400w HPS? I have a small amount of lady hairs on all my Great White sharks and I'm still feeding them Biobizz grow, should I start with the Biobizz Bloom now and swap the lamp or give them a bit more time?

Thanks

Bazza

Most growers switch, when the stretch appears to be over. Some wait 2-4 weeks, into 12/12 cycle. Some switch immediately.
Same thing with bloom nutes, some wait about 2 weeks.

I'm going all the way with a ceramic metal halide.