Rooftop Lily Ponds: A Beautiful Partnership Between Fish and Water Lilies

When you step out on a city rooftop, your brain makes the appropriate preparations for the sensory overload to come: the deep growl of traffic far below, the droning whir of AC units, and a steady breeze carrying the scent of sun-warmed asphalt. But if you venture past a cluster of potted ferns and bamboo planters on a green roof, you may well stumble across something truly amazing that can only be seen five stories above the earth: a quiet, dark pool of water with saucer-sized emerald pads covering it, streaks of living color sliding silently through the depths.

The Beauty of a Lily Pond in a Rooftop Garden

A lily pond nestled up high in a rooftop garden is one of the most surprising delights in the landscape of the modern city. At the heart of that delight are the multicolored fish, the little swimming gems transforming what could have been nothing more than a still basin of water into something alive and self-sustaining.

Colorful Fish That Thrive in Rooftop Ponds

To the casual observer, watching these creatures laze about the floating blossoms is pure indulgence, but there is clever, practical nature to be found beneath the surface. Most rooftop ponds avoid the delicate demands and picky care of tropical species that require heated aquariums. They turn to hardy, cheerful varieties that can thrive outdoors without fuss: spotted Shubunkins with their calico mix of sky blue, rust red, and midnight black; two-tone Sarasa comets that look like miniature red-and-white torpedoes; and, in deeper basins, young koi bearing bold strokes of gold, white, and ink.

Against the dark, shady bottom of a pond and the bright leafy canopy above, the vivid colors perform a kind of magic. Sunlight falls on the water, and then all at once an orange flank blazes to life, disappears beneath the umbrella-like pad, and reappears as a flash of snowy white on the far side.

The Natural Partnership Between Fish and Water Lilies

What makes these fish so enchanting above all is that it is not the fish that are the marvel, but the silent partnership between the fish and the lilies. Rooftops have always been notoriously harsh places. They get blasted with punishing, direct sunlight, hit with sudden gusts of wind, and superheat at a much faster rate than gardens at ground level. If you leave an open bowl of water on a bare roof in July, you'll have warm, soupy green slime in a week.

How Water Lilies Protect Fish and Keep Water Cool

That's where the water lilies come in as the unsung heroes. Their wide, leathery pads cover the water's surface like living parasols, blocking away harsh UV rays and keeping the water considerably cooler than the surrounding air. By stopping the direct penetration of sunlight, lilies stop the explosive algae blooms before they can begin. Behind them, their sprawling root systems turn into a jungle gym of underwater stems where the fish can dart about to rest, cool off, and escape curious rooftop visitors such as crows or gulls.

How Fish Benefit Water Lilies and Prevent Mosquitoes

The fish turn the favor back around most generously. Rooftops are magnets for stray mosquitoes laying eggs in still water. To a hungry goldfish or Shubunkin, those mosquito larvae are nothing but an all-you-can-eat feast. A few fish guarantee that a rooftop pond is never going to become a mosquito breeding ground. Meanwhile, their natural waste falls down to provide organic fertilizer, enriching the hungry lily roots in clay baskets along the bottom. It's a closed, miniature circle of life; the plants protect the fish from heat and the sky, and the fish in turn feed the plants and protect the water.

How to Create a Rooftop Pond

People always imagine that putting a pond on a roof involves an engineering degree and a crane, but today, modern container ponds have made it easy as pie. With lightweight composite tubs, pre-molded fiberglass, or insulated cedar troughs, gardeners can create flourishing miniature wetlands without exceeding the building's structural limits. A simple submersible pump or a small solar-powered fountain is all that is needed to keep oxygen circulating in the water, while the lilies and gravel take on the heavy work of biological filtration.

The Peaceful Beauty of a Rooftop Lily Pond at Dusk

Besides the biology and mechanics of the rooftop pond, there is a very deep emotional draw to simply standing beside it at dusk. Below the parapet wall, the city races at breakneck speed; commuters hastening, headlights streaking, sirens echoing among the high-rises. But bend over the edge of the pond and time comes to a complete standstill. The water lilies close their petals gradually as the sun goes down. A spotted fish glides lightly up to the surface, and it's mouth makes a small ripple that sends a ring of liquid gold shimmering out toward the leaves. In that peaceful little corner between the concrete and the clouds, you are reminded that it takes no great forest for nature to work its magic. Sometimes all you need is a shallow tub of water, a few floating leaves, and a dash of bright color swimming in circles across the sky.