I'm not sure what you mean by a heat type bulb, however I doubt that 15 watts is going to be enough for what you're wanting to do. I'm running 36 watts over my 5.5 gallon, and I wouldn't even call it high light based on plant growth. You need more light to hit the various lighting levels on these smaller aquariums. Dwarf Hair Grass requires a lot of light to grow well, and generally isn't a good plant for getting a planted aquarium balanced since it is easily over run by algae. You'd be better off starting with fast growing stem plants or floating plants. Once the aquarium has matured you could give the hair grass a try.