It has the color spectrum for growing plants (6000K) and adjustable percentages to lower and up the amount of light.
Watts per gallon may not be exactly what you need, PAR (photosynthetically active radiation), might not either, there is a need to know which colors are in the full spectrum colors in the light, as in the K
There have been some people who do testing on the lights and find out the charts if not supplied by the light maker. Not my ability, so I go from what the company information supplied.
In aquarium lighting fixtures, not always but often for aquarium plant growing they will show a chart in which shows the actual light which is being sent to the plants.
Below - If you see after scrolling down, to the light color chart, that is an example of something which would be pretty good for plant growing.