IMac – How to stop the iMac’s remote management connection from defaulting to wifi

You could use the iMac to remotely connect to the mac mini over the network with apples remote desktop software. If you have a gigabit wired network between them then performance would probably be good enough to be usable for most tasks except 3d gaming or hd video I'd say. You cannot directly attach the iMac as an external display using a video cable however. Also, remote desktop access over wifi would probably not be ideal for everyday use

To actually perform this, just do the following:

1. In Finder, click the 'Go' menu option and then 'Connect to Server'
2. type in vnc://mac-name.local:5900/ or vnc://mac-ip-address:5900/

This will connect the two computers and you sign in with the credentials of the account on the remote Mac

This is happening because the two machines are not on the same subnet.

The G5 is on the Mac Mini's subnet, while the Mac Mini is on your Wi-Fi's subnet. The IP address of the G5 has been handed out by the Internet Sharing DHCP service on your Mac Mini, while the Mac Mini's IP address has been handed out by the DHCP service on your router.

Your best bet would be to connect your G5 via Ethernet to your router.

If that is not possible because of location constraints, there is a piece of software for Mac called IPNetRouterX that may do the job. It allows Ethernet bridging, which is what you want. The only problem with this software is that it costs money. It seems like there might be a free trial of it, however.