get yourself a Metal Halide, or High Pressure Sodium, that mercury vapor lamp you got (I think its a merc) isnt proper for gro'n.

got a few bucks, like 30? go to www.homedepot.com and in their security lite section they have a 70watt HPS for approx 30 bux (last yrs price), that'd be more than enough for 1 plant.