Koi Pond, an iPhone app favorite, is now available for the iPad as Koi Pond HD. Even if you couldn't care less about real fish, the app's gorgeous graphics and crazy level of customization should convert any koi-skeptic.
In addition to the satisfyingly realistic physics of the fish, of which there are several breeds, Koi Pond HD gives you full control of your pond, letting you choose everything from the placement of its plants to the exact hue of its ambient lights. I don't know why it's so satisfying to curate a perfect little koi pond to your own specifications, but it definitely is. $2. [iTunes]