From Everyday Software:
Maquarium is aquarium management software for the novice or expert fish keeper. It allows users to track chemicals, schedule tasks, keep notes, and manage inventory. Maquarium features a fish profile database, which is always being updated and helps you track and maintain the delicate needs of all the fish in the tank. Furthermore, Maquarium helps the novice by warning users of dangerously high chemical values and the recommended course of treatment.
Version 1.7 adds the following: Added complete support for Panther. Added better error checking when trying to graph invalid dates. Double-clicking aquarium conditions now goes to edit mode. Overdue Notification window no longer takes focus when shown at startup. Added several new fish profiles to the fish profile database.