Although all AeroGarden Classic 7s are identical on the outside, there is an important difference in the internal technology that will affect how you maintain and service yours. Here's what you need to know:
The roots of plants grown aeroponically or hydroponically require oxygen and water for healthy growth, and AeroGrow has developed two ways of oxygenating the water in the AeroGarden water bowl. One is a water pump inside the bowl that circulates water through the Grow Deck. It flows out of a little spigot in each of the seven holes in the Grow Deck and drops back down into the water. The other uses an air pump in the AeroGarden Base that pushes a small amount of air ithrough an airstone inside the Water Bowl which emits a froth of tiny bubbles. Both systems work great for growing plants.
All AeroGarden 3s and 6s use the air pump technology. All "tall" AeroGardens, such as the Ultra, the Extra, and the Extra Elite, use the water pump technology. The AeroGarden 7s, however, might use one or the other.
How do you tell which one you have?
The easiest way is to unplug the AeroGarden from the wall and lift the water bowl up and off the base. The AeroGarden 7s with the water pump will have two brass strips side by side on the lamppost behind the bowl:
By contrast, the lamppost on the AeroGarden 7s with the air pump is unbroken smooth plastic.