Mechanical fish tank

Mechanical fish tank: A layout capable of running trains in lazy, never ending loops to provide background ambience in a room.

Usage: Jane turned on the mechanical fish tank and dimmed the room lights before the guests arrived.

Source: Discussed at around the 15:35 mark in the accompanying video. John Kit notes it's a common practice with model railroaders, and wonders how something similar could be adopted by slot car track owners. Mr. Kit also states that the mechanical fish tank concept wasn't unheard of in slot cars' earlier days of model motoring.

from the electronic files for the 2029 4th edition of The Dictionary of Non-Existent Model Railroad Terms.