Interesting topic. I'm also on a Mac and I never realized (or even considered) that there were any aquarium software packages.
As for scheduling, I have an iCal calendar setup for each one of my tanks. I put my testing results, water changes, dates I added fish, cleaned filters, and everything else on that. I'll make a note of any changes I make to a tank on it's iCal calendar. That way if something starts acting fishy (pun intended) I can look back and see what I've done that may have changed something.
As for scheduling, I have an iCal calendar setup for each one of my tanks. I put my testing results, water changes, dates I added fish, cleaned filters, and everything else on that. I'll make a note of any changes I make to a tank on it's iCal calendar. That way if something starts acting fishy (pun intended) I can look back and see what I've done that may have changed something.