Michael R. Bloomberg loves tropical fish. So when he was elected mayor, he installed two giant aquariums in City Hall.

The cost to him for having the tanks cleaned out every week for the past 12 years: around $62,400.

The mayor likes to nosh, too. So he paid to feed his staff daily a light breakfast (coffee, bagels, yogurt) and a modest lunch (tuna salad, PB&J, sliced fruit).

The bill for his entire mayoralty: about $890,000.

Mr. Bloomberg, above all, enjoys hassle-free travel. When he took his aides anywhere, from Albany to Athens, it was by private plane.

The price tag for all that jetting around: roughly $6 million.

When Mr. Bloomberg leaves office at midnight Tuesday, he will bequeath a litany of record-shattering statistics on crime reduction, sidewalk safety and skyline-altering construction. But perhaps the most staggering figure is the amount of his own money that he devoted, day in and day out, to being mayor — much of it unseen by the public.