Opening the blind may cause algae problems? If not yes sunlight is best. Is it just a regular fluorescent fixture with no reflector? The light needs to be down close to the plant. If no reflector you can but a reflector to install in the fixture or just go ghetto and use aluminum foil. Get a good daylight bulb for it from the hardware store if it just has a regular shop bulb. Another option is to buy a cheap clamp lamp or for more money get a hanging pendant fixture with a good reflector and put a good bright daylight compact fluorescent bulb (there are decent ones at the hardware store) and put it close to the plants.