If you dont want to get a hood, then be careful that there is nothing around to get into the water (and that none of your fish are jumpers!)
a normal bulb would be fine, say if it was for a betta tank, but if it was for a larger tank then it might not give enough light, especially if you were growing live plants.
You really want a light over the tank. Your fish orient their topside to the lidht as if it were the sun. A lamp next to the tank would have them all swimming crooked.