I'm currently running a NutriGrow F15-T8 bulb on my 20 gallon tank. I
keep java ferns in the tank and they generally go downhill. They do it
slowly so it's not a huge problem, but it would be nice to have them be
healthy and last longer. btw, I stick with java ferns only due to the
low wattage per gallon. So my question is, what is the best bulb for
this situation? Should I switch from NutriGrow to something else?

thanks,

Dave