I'm working with 1 15 watt t-8 bulb. The tank does not get any extra light and can't be moved, but I think I can get an 18 watt bulb if it helps. I have 1 inch of soil and 1 inch of the smallest grade gravel I could find. I have duckweed as the floating plant. I'm looking for stemmed or rooted plants that will grow well in these conditions.