There is a website which allows you to keep track of your aquarium online.
The website is called Reefiris and is currently in Alpha mode which basically means that there may be some bugs present and some features which are not yet complete. As the site is in Alpha mode the data entered may be deleted to allow for enhancement, bug fixes etc to be applied.
Once the website comes out of Alpha mode and enters beta stage it will probably be more stable.
To start tracking your aquarium you first need to sign up and then enter details about your aquarium. Once this is done you can start logging parameters, reminder notes etc. The good thing about it is that you get your very own web space where you can see all of your parameters over time in a graphical format (hourly, daily, weekly and monthly). Therefore you can spot trends starting to appear and hopefully react before it becomes an issue.
They also appear to have support for various controllers such as Aquatronica, AquaController etc so if you use one of these the data can be exported straight into Reefiris.
I think that this site has amazing potential and if done right could be an exceptionally useful tool for aquarists all over the world.
Why not go and check it out and remember to keep an eye on it as I’m sure it is going to improve.