I recently upgraded the light over my 20G from a 65 watt PC 6700K to a 70 watt 10000K Metal Halide. I'm super happy with the light but I'm trying to get a sense of how much more light I have. It seems quite a bit brighter than the PC, more than just a 5 watt difference. The MH bulb output is supposedly 3100 lumens. Any idea what wattage fluorescent bulb this would be comparable to? Watts per gallon generally refers to fluorescent lighting, so I'd like to know roughly what I have.