You will probably need to go to an actual pet store to find aquarium light bulbs. Unless your Walmart has a pet section, they probably just sell house lamp type bulbs.
An aquarium bulb will not be a spiral, but it'll look like two U's coming out of the part that screws in. Like this:
Zoo Med Ultra Sun Daylight Compact Fluorescent Bulb at PETCO
An aquarium bulb will not be a spiral, but it'll look like two U's coming out of the part that screws in. Like this:
Zoo Med Ultra Sun Daylight Compact Fluorescent Bulb at PETCO