The computer to run the Aquarium on the plasma only costs about $500.

The plasma, you have to add a zero or two.
Also, you can tweak Aquarium settings with the keyboard. Press "A" for a list of them. For example pressing LEFT and RIGHT arrows to fiddle with the background color rather than having to manipulate in the Settings window and then Exit to see the effect.
Pressing W also seems to garner responses from onlookers.