If you're using the Fluval Aqualife and Plant LED then it's probably fine for a low light setup in a tank like that, with so much depth to the substrate it probably puts you right in the middle or possibly towards the low end of low light. Personally, if I was setting up a low light setup I would probably still have pressurized co2 for algae control and general health of plants. If you're willing to spend the extra money for a pressurized co2 setup then you will have healthier plants now and you would be free to increase your light later if you choose to.