Aquarium Desktop 2009 comes with several fish included in the base package.

Users can choose which fish to display on their desktop and even have multiple fish of the same breed. As a result, user can have as many or few fish as they want swimming around in a realistic environment. It also comes with a host of different plants that, like the fish, have been rendered from 3D models for very lifelike animation and detail. Aquarium Desktop also comes with multiple wallpapers, aquatic sound effects, and more.

The program is highly configurable. Plants can be re-sized, sound effects can be added or disabled. In addition, Aquarium Desktop is designed to be intelligent in its CPU usage. If the fish are covered (for example when a window is maximized) the rendering goes into idle mode so that the fish don't slow down your computer. The graphics are also compressed in memory to minimize how much memory it's using.