My Aquarium is an iPhone app that comes with selectable gravel (5 colors), selectable backgrounds (5 types), selectable fish (30 types), and selectable decorations (13 types). This means you can customize your own aquarium any way you like it. The aquarium will be restored exactly the way you left it the next time you launch it.
Here is a video demo of My Aquarium on the iPhone
This 3rd Party App is available at the Apple iTunes AppStore. Browse the full list of all AppStore apps filed under the AppStore category.