A fishbowl does not necessarily need an air pump, but it ultimately depends on your setup. Some equipment might require an air pump, which means you need to properly plan what you want to get. If you already have a filter in the bowl that is run by an air pump, then you must have an air pump. Without an air pump in place, the filter will not work and you won’t gain any benefit from having just the filter on your tank. If your bowl has an action ornament that is run by an air pump, you will also need an air pump that will help it operate. If you’re thinking about getting an air stone decoration that gives off a cascade of bubbles, you will need the air pump to run it.