Communicate between 2 arduinos 30m apart

I am wondering the best way to communicate between 2 arduinos. probably a micro & mega. is RS 485 the way to go or ethernet
I need very reelable fast communication
Thanks Russell

If you're looking for a wired connection, Ethernet would be very fast and reliable. However, you would need to have some understanding of networking to use it.

What do you mean by "fast communications"?

RS485 plenty fast for that distance.
Use regular serial comm's, at 115200 or 230400 at each device with MAX485, MAX488 for the RS485 level controls.

See page 8.