Sorry to get technical Tank Girl, but I believe what Wavetide is talking about is actually the starter. Ballasts are much larger and heavier. Also They were used on older, and cheaper (sorry WaveTide) fluorescent fixtures. If your fixture is the type where you have to press a button until the bulbs start to glow it has no ballast, and that piece is the starter. What a starter does is does is it builds up an electric charge to ignite the neon gass in the tubes. In addition to pushing it back in it should also turn about 1/8 turn to lock it in place.
Aquarium: 55 gallon with 60 lbs fluorite 20 lbs gravel
Filtration: Eheim 2026 Pimp #168 with Fluval surface skimmer
130 watts of 6700k PCs 12hours, 130 watts 10K 4 hours.
Co2 suppl.: 10lb tank with Milwaukee al in one.
Flora:Java Moss, Water Sprite, Microsword, Anacharis, Water Primrose, Rotala rotundifolia, Cryptocoryne wendtii, Echinodorus x barthii, Bacopa monnieri
Fauna: 3 Sailfin Mollies, 8 Tiger barbs, 6 Cory Julii, 6 Ottos, 2 SAEs, 9 Amano shrimp.