Some plants will grow in almost no light, they tend to be the slowest growing, and often the longest standing in the hobby.
The more light, the more need for ferts. Generally it's not a bad idea to dose the micronutrients in any planted tank. A 15W T8 tube would certainly foot the bill, or similar in other tubes, like the arcpod lights.
Depending on how you're mounting it, you may find that the 15W, 18" tube fits better.