There exists evidence that cannabis grown at altitude is stronger than that grown at sea level. The theory being that the trichome is a sun screen, with resin production related to intensity of UV. Cannabis Botany texts refer to such. If so, then adding more UV to a tent will have the same effect resulting in stronger buds.
When choosing MH or HPS, the lack of lumens for the same power is evident in the MH. Ahah but lumens are not PAR you may say. Yet the HPS spectrum is a better fit for the main chlorophyll receptors too meaning bigger buds. Not much in favor of MH so far. The show stopper fact is that normal glass is entirely opaque to UV light. UV bulbs have to be made with special glass to let it through. Thus you are supplying more blue to your plants via the MH but no UV.
Reptile bulb CFLs produce UV light which the reptiles need. They also have another peak in the blue. Thus they are perfect compliment to the spectrum of a HPS. They give you both the UV and the blue that the HPS lacks. They are cheap, they consume little power. For those that want pure UVB, there are the philips narrowband UV tubes, sold as psoriasis lamps. Avoid UVC lamps. These are sold for water sterilisation, the light directly damages bacterial DNA, it will do the same to you too.
