I have a 30 gallon tank with 20 watts of light. I have had this setup for about 8 months, and while I have been able to keep plants alive, they grow *really* slowly. What has done best is java fern and anubia. Everything else is slowly dying, while the anubia and fern are holding their ground. If you are serious about a planted aquarium, I strongly recommend upgrading your light. I am getting ready to move and when I do I will have my tank in front of a window.