Oh. The air pump I'm using uses 2.3W XD.
so the air pump costs $0.25 cents per month
the laptop at 90 watts costs $9.72
that's also assuming its draining the full 90 watts 24 hours per day.. its likely using around 10 watts at idle if the screen is on
so unplugging it will likely do no good
turning the heat down 2 degrees on the a/c unit will likely bring the same monetary gain as not having ur tank FYI
you can also open the window screens during the day to let more heat in, and at night close them to prevent drafts and heat loss. little things help