I downloaded one from this site and found it to be rather good. I then realised that if you already have Excel on your computer you can pretty much do it all in Excel and make some excellent graphs to boot of your water chemistry. (If you don't have excel, openoffice's spreadsheet application is almost completely compatible. In fact, I think it would be fun to make some excel templates available to aquarists.
With regard to automating an aquarium, I had something quite different in mind. I thought that one might be able to come quite close to replicating the seasonality of an Amazon tributary by changing the water flow and temperature, similulating the changing lighting conditions, salinity and so forth and see if you couldn't get some real troublemakers to spawn for you. And then there is the concept of the automated water change. Now that would be great!!! Jeff
In theory there should be no difference between theory and practice. In practice, there is.