I've found this T12 fluorescent bulb to be very efficient for plant growth. They have been installed for a bit more than a week and plants are already giving positive response to it. Only Cons seems to be the availability of the product. They are said to be rare to find since this product can be found in hardware stores (well, used to be).

In the end, I would recommend to any T12 x 24" owner to switch to theses if they are trying to promote freshwater plant growth.