I agree with Red1313
Incandescent light bulbs aren't very good for the aquarium. They give off SO much heat, and not as much light. Fluorescent light bulbs are much better for the plants and the entire tank

My plants always died when I first had Incandescent light bulbs. Although when I bought my 29 gallon tank, I could have full spectrum Fluorescent light bulbs

So I put in some new plants, and they flourished well

Just a little bit of fertilizer twice a week, and they were just thriving
Although my 10 gallon tank didn't survive well until I put in fluorescent lights that were fit for a 10 gallon tank

So then I didn't have to worry about my plants dieing and me having to transfer them into my larger tank
I hope you have a fluorescent light bulb in for your 5.5 gallon tank!
Good luck!
Neji