From the getting started ->quick start section of the AquaNotes help file:
Follow the configuration steps below to setup AquaNotes for a Ethernet connection (AC3, AC3PRO):
1. Select the menu choice 'Database->Tank Database'. Update the Serial field on this window with the serial number of the AquaController. The serial number of the AquaController can be found performing a self-test. The serial number that should be entered is shown on the bottom line of the AquaController's self-test display (Passed #WXYZ).
2. Also on the 'Tank Database' form choose the 'Config' tab. Select TCP (Aqua3) button. Enter the IP address, login, and password of the AquaController 3.
3. Now select the menu 'Status->Reef Tank'. You should get a window which displays the current status of the tank and the controlled devices. If you get a message 'AquaController not responding', something is not configured correctly. Re-check the cables, and the AquaNotes configuration which is described in the previous paragraph. If you are still having trouble refer to the AquaController Not Responding trouble shooting section.
Curt