My Aquarium is a virtual aquarium. You drop dish, vegetation, and things like sunken ships into a tank and then watch the fish swim around in it.
The app gives you a big tank and the ability to stock it with a large quantity and variety of fish. You can also drop vegetation or objects such as sunken ships and divers into it. You can then move these around the tank. While you can pan around the tank so you can see all parts of it, you can never see it all at once. There is no zoom support, though you can view the tank in either portrait or landscape mode.
Adding fish or items to the tank is done through a button for each, and it just randomly adds them in. Two more buttons remove all of the fish or all of the objects. You can also click a button to randomly change the entire tank, and you can toggle between five backgrounds via yet another button. Last but not least, the toolbar these buttons appear on also gives you the ability to toggle sound on and off. This toolbar can be turned off and fades out so you don't have to look at it while viewing the tank.
I suppose the intent of My Aquarium is to entertain you, which seems fine for a desktop application where power consumption is not a concern. In the case of the iPhone, though, battery life is of the utmost importance. This makes the usefulness of such an app suspect, and one wonders who would really want to spend time watching a virtual aquarium on an iPhone. If it at least let you disturb or otherwise "mess" with the fish, it could be considered a toy or amusement, but as it stands, it's simply there so you can watch it.
Is My Aquarium for you? If you're looking for a toy, this isn't really it. It is strictly a simulated tank with a well working but limited set of features. If that sounds good to you, it's inexpensive enough to experience.