Frontiers of Science:
Mission Impossible:
Building a Backyard Ocean

Written by Dr. Sherwood B. Idso

To assist scientists in their study of terrestrial (land) plants and animals, a number of excellent zoos and botanical gardens have been developed. And to study aquatic organisms that inhabit freshwater lakes and streams, many large aquariums have been built. However, attempts to create similar large facilities for the study of marine or saltwater creatures have always met with frustration; that is, until recently. For on October 15, 1980, the Smithsonian Museum of Natural History in Washington, D.C., opened its doors to a new 3,000-gallon piece of transplanted ocean that is home to over 200 species of marine plants and animals, including about twenty different types of living corals. And that was a real accomplishment, because living corals had never before survived for any length of time in an aquarium completely isolated from the sea.

When my family and I read of this feat, we decided that we would try it too. Our first step was to write to the Smithsonian scientists for advice. We waited anxiously for a reply; but after a couple of weeks without hearing from them, we decided that they probably thought we were not serious about it. So we tried another approach. I had to attend a meeting of scientists at the Scripps Institution of Oceanography, so I took two of my young sons with me. While there, we visited as many marine biologists as we could, getting tips on how to proceed. After some discussion with them, the best advice they could give us was, “Don’t try!” Well, their negative advice only heightened our desire to take up the challenge.

Since our home in Tempe, Arizona, has a very mild climate, we decided to construct an outside pond rather than an indoor tank. Our first step was to dig—and dig and dig. Every member of the family helped at one time or another, as did many of the neighborhood children. We not only had to excavate a basin for the water, but also a much deeper hole for an underwater viewing chamber.

We started near the end of November, and about a month later the excavation was complete, including the viewing chamber and a twenty-foot arching bridge that spanned the two-lobed basin at its midpoint. We waterproofed the sides of the pond by laying five layers of black polyethylene plastic over the soil. Then came several trips to the dry bed of a nearby river, where we collected thousands of pounds of smooth, round rocks to put on top of the black plastic. These rocks were then covered with fine sand—fourteen tons of it.

Last of all, a friend of ours helped us install a pump and sand filter to circulate and purify the water. Initially, all this system consisted of was an intake port at the bottom of the pond and a return port beneath the center of the bridge. Later, however, we expanded it to include a return port at the deep end of the pond and another at the shallow end. Then, since the shallow end had an island in the middle of it, we built up two ridges of river rocks between this island and the pond’s banks to create a tidal pool into which the shallow return port would empty its water.

Lining this pool with crushed seashells created another filtering system, as the water entering the tidal pool had to flow through these shells and rocks to reach the bottom of the pond where the pump withdrew it.

In addition to water impurities, another problem we had to worry about was temperature. It seemed likely that the pond would probably get too cold in winter and too warm in summer. About that time we read where the Steinhart Aquarium in San Francisco had just installed the first solar panels ever to moderate the temperature of a saltwater tank. So as in the case of the Smithsonian Museum, we again asked, “Why not us?” And two weeks later we had our own solar heating and cooling system ready to go.

The last bit of construction was a four-by-six-foot piece of plywood supported by four redwood supports in the deep end of the pond. It protruded about six inches above the water surface, and to it we strapped several long palm fronds to provide a place of shade and refuge for those sea creatures that shun the sight of humans. Then, a twelve-inch diameter plastic pipe was positioned at the bottom of this area and partially covered with rock and sand to create a cave for extremely reclusive creatures to hide in.

Finally, everything was ready. It was time to fill the pond and hope that there were no leaks. Since we wanted to know how much water it held, we checked the water meter to our house and then turned our hose into the basin. Several hours later when the water reached the top of the surrounding banks, we calculated a volume of 4,000 gallons—larger by a good margin than even the Smithsonian’s system.

In the midst of our initial success, however, we still had some reason for concern. Water began to seep into the observation room from around the viewing port. After a few hours, though, it subsided, probably due to the wood swelling when it became wet. Fortunately, it has not leaked since.

The first creature to inhabit our pond was a small dime-store turtle, secretly supplied one night by one of the neighborhood children. Then came fifty black mollies from a local aquarium shop. All of them did extremely well as algae began to grow in the pond, and several different types of aquatic insects appeared. Still, the pond was just a pond. We had yet to add the synthetic sea salts that would start it on its way to becoming a true marine ecosystem.

Join with us next month and read about this conversion process and the first of our several trips to Mexico and the Gulf of California, where we collected specimens for our “backyard ocean.”

Photographed by Dr. Sherwood B. Idso

Our first view from the underwater observation chamber, showing a few black mollies.

1. We started with a barren piece of ground in a corner of our backyard.

2. After a month of digging, the basin was finished along with the underground observation room.

3. We covered the basin with five layers of black plastic film, thousands of pounds of smooth, round rocks, and fourteen tons of sand.

4. A picture taken from the roof of our home shows the pond just about ready for water.

5. Two solar panels were installed to warm and cool the water.

6. The pond was fenced in for safety reasons, and palm leaves were lashed to a support in the deep end of the pond to provide a hiding place for fish and other creatures.

7. A view into the underwater viewing chamber taken just before the pond was filled with water.

8. A friend of ours helped connect the solar panels to the pump and filtering system.

9. We watched intently for any leaks when we added water from the hose.

10. The few initial leaks soon stopped; and when the pond was filled, it was determined that it contained 4,000 gallons of water.