A clean-edged, concrete-lined pond looks just right in a formal, brick-paved herb garden. This pond, the centerpiece of a patio, was dug by a backhoe. Wooden forms strengthened with rebar were set into the 8-foot-square by 4-foot-deep hole, and the pond was lined with concrete. A drain prevents overflow, and a waterproof electric connection under the brickwork powers the fountain and recirculating pump. Pots of lilies and goldfish add color. After 18 years of operation, the pond no longer needs annual cleaning. The plants, fish and aerating fountain together create a self-sustaining ecosystem.