After a couple weeks of progress, Aquarium is now on the android marketplace! Like my other wallpapers, there's both a free and donation version, with the donation version gaining a settings menu.
The settings menu in the donation version gives you access to a couple more fish than you see in the free version, and lets you select from four different backgrounds (one of which is a non-busy waterscape, if that's your thing). It also lets you turn on or off the overhead light.
Let's actually discuss the settings screen for a bit. Originally I had a grandiose plan to let you hand-place fish and plants as though you were actually assembling a fish tank. This is a cool thing to do, but pretty quickly started making the UI cumbersome (drawer-style menus, drag the fish to where you want it to be, etc).
I realize that with most things of this nature, the settings screen is not a common-usage item. In my experience, at least, you'll tend to find a setup you like and stick with it for quite a while. With that in mind, I decided to have the menu randomize the placement of fish and plants. Tap it a few times until you find a mixture you like, then hit back and it'll remember those settings. This kept the interface very simple (and easy to understand, as well) but still gives you the same breadth of options in most regards and doesn't take long to work with. I feel like this was a good compromise between simplicity and the original goal.