Better lighting

[fishb0ne]

I have a standard 20 gallon tank with low light plants, just some crypts. I'd like to give them a boost in growth so naturally that means better lighting. I am currently using an Aqueon light fixture with a generic T8 full spectrum light bulb, 15w.
There aren't any larger light bulbs.
What better bulb should I get? Would somehing like a Zoomed T5 be better?
I noticed the light strip doesn't have any sort of reflector in the housing. Is it worth the effort to make one? Not sure what to use.
I was also suggested trying 2 light fixtures but if I can avoid that unsightly proposition, the better

 

[jetajockey]

The easiest method is to get a new fixture, you can't put a t5 into a t8 fixture for example. There are some really cheap 2x24w t5ho fixture on ebay (oddysea) that will be more than enough to get the job done and very affordable.