You mean sunlight that lights up a room, but is not directly on the tank?
I would say it depends on how much light, which is not a good way to go about it. We need a way to measure how much natural sunlight is entering the tank, and without knowing how, it would be hard to know for sure.
In a planted tank, people go by Watts.
I would probably have to say no, as you should get some decent lights for your tank.
-FHM