In terms of water chemistry, it shouldn't be a problem. There are many species of plants that live in fairly acidic/soft conditions like you would find in blackwater. That being said, there will be a reduction of light due to tannins in the water. The exact amount would be proportional to the amount of tannins in the water. If you have really dark water, then it might be difficult to grow much of anything in the tank.
Are you doing this with a biotope in mind? There are a good number of very low light tolerant asian species that would do ok assuming you don't have too many tanins and you start out with a reasonable level of light. Crypts, ferns, and anubias will all work well for this. If you have a deeper tank (29, 55, etc) with only T8/T12 or single/double bright LEDs, you might find yourself wanting more light.
