I used to keep a reef tank (100 gal). It's kind of the inverse of a boat - where a boat is a hole in the water that you throw money into.

The tank's been gone for over 20 years now. The only thing left is the light fixture (which is now used to illuminate part of my workbench) and miscellaneous bits of piping, tubing and empty test strip bottles (they make great storage containers).

It was really cool when it was doing well - it sucked when the back glass separated from the tank - for the second time. I said, "No more!"