Welcome to CannaCom...TsarBomba...:thumbsup:

Do you know the kelvin temp of your Metal Halide bulb?...most MH bulbs run from 6500k down to 4100K. The 'warm MH' bulb is the better all round bulb for flowering...(4100k-5000k)...:thumbsup:

The higher the kelvin temp ...the better it is for vegging...(5000k-6500k)

I would flower with a 4100k MH bulb and veg with a 5500k MH bulb...

Hope I didn't confuse too much?...imp:...a conversion bulb is the next best option...good luck...it looks nice so far...