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That 20 watt rating is the rating for the starter, which is what is marked as 20 watts. The mod takes all of those components out and replaces the whole mess with just sockets for the screw-in bulbs. So, physically you can modify this the same way I did.
You should remember though, that my modified light does not light up a ten gallon tank enough to grow much more than low light plants. And, I am using 20 watt bulbs in it, not 14 watt. A 15 tall tank is 17 inches deep, as I recall, so you need a lot more light than is needed for the ten gallon tank, which is only 12 inches deep. Subtracting 2 inches for substrate depth, the tanks are 10 and 15 inches water depth. Those screw-in bulbs lose intensity proportional to one over the depth squared. That means to get the same light intensity at the bottom of the tank (top of the substrate) you need 15/10 squared times as much wattage, which is 2.25 times as much. To get the same amount of light as I have you would need 90 watts of the screw-in bulbs. I suspect that isn't possible without adding a cooling fan to avoid melting the plastic.
I think you will need to either make a new light fixture, to use PC bulbs or T5 bulbs, or buy a new fixture. One advantage of doing that is that the linear tube bulbs only lose light intensity with depth proportional to one over the depth (not squared), so you need much less wattage of bulbs to get the same light.
Another problem with the retrofit I did is the small "aperture" of the light. All of the light has to go through the rectangular opening in the plastic hood, limiting the light considerably. If you made a light fixture or hood that covered the entire top of the tank you could probably get enough light from screw-in bulbs, providing you used at least 4 of the 20 watt bulbs, and with the larger volume to fit the bulbs in, they would stay cooler and possibly not need a fan.
You should remember though, that my modified light does not light up a ten gallon tank enough to grow much more than low light plants. And, I am using 20 watt bulbs in it, not 14 watt. A 15 tall tank is 17 inches deep, as I recall, so you need a lot more light than is needed for the ten gallon tank, which is only 12 inches deep. Subtracting 2 inches for substrate depth, the tanks are 10 and 15 inches water depth. Those screw-in bulbs lose intensity proportional to one over the depth squared. That means to get the same light intensity at the bottom of the tank (top of the substrate) you need 15/10 squared times as much wattage, which is 2.25 times as much. To get the same amount of light as I have you would need 90 watts of the screw-in bulbs. I suspect that isn't possible without adding a cooling fan to avoid melting the plastic.
I think you will need to either make a new light fixture, to use PC bulbs or T5 bulbs, or buy a new fixture. One advantage of doing that is that the linear tube bulbs only lose light intensity with depth proportional to one over the depth (not squared), so you need much less wattage of bulbs to get the same light.
Another problem with the retrofit I did is the small "aperture" of the light. All of the light has to go through the rectangular opening in the plastic hood, limiting the light considerably. If you made a light fixture or hood that covered the entire top of the tank you could probably get enough light from screw-in bulbs, providing you used at least 4 of the 20 watt bulbs, and with the larger volume to fit the bulbs in, they would stay cooler and possibly not need a fan.
