The LED tubes produce more light with only half of the watts used. The 24″ is 10w while the 48″ is 18w. Normal fluorescent tubes produce light all around the circumference of the tube and much of this light is lost unless you have adequate reflectors to focus the light towards the target, with the LED tubes though there is no need for reflectors to be installed or used because the light is already focused. This results in much better light penetration of the water column.