The swimming pond -Summer 2010

I’ve had several recent inquiries about my swimming pond, so I figure that it’s about time for an update. This is my favored spot in the garden, where I spend my most relaxed time, and (on rare occasions when I’m sociable) where my wife and I entertain friends and family.

There are six ponds in the one acre garden, one a dirt bottomed wet weather pond, four small ponds with streams and waterfalls, and the swimming pond, though this is a bit of a misnomer since I’m too lazy to swim. Instead, slip into the back garden on any summer weekend day and you’re likely to find me floating on my inflatable lounger, hungry koi circling like sharks.

The swimming pond was constructed in 2006, is nearly forty-five feet from the waterfall to a shallow filtration area, and thirty-five feet wide. The depth varies, but is four and a half feet at the deepest point.  The pond is lined with EPDM rubber, and a boulder and river gravel covered shelf along the edges just below the water line hides the thick black rubber. The bottom of the pond is covered in small tumbled stones with no sharp edges that could pierce the liner.

Filtration

There are two sections to the pond, the main area of deeper water, and separated by a stone wall a few inches below the water is a two hundred square foot area filled with small bluestone gravel. A submersible eight thousand gallon per hour pump housed in a box with a skimmer door at the pond’s edge delivers two-thirds of its flow to the waterfall, and a third to flexible PVC pipe that is perforated at twelve inch intervals and buried beneath three feet of gravel so that water flows up, and is filtered by the gravel.

When I was preparing to build the pond I researched the limited resources available, and discovered that most swimming ponds have almost fifty percent of their water surface devoted to filtration. In my limited space a filtration area that large would leave too little area for deep water, so I modified the filtration design to less than fifteen percent of the pond’s surface area.

I don’t test the water, and I’m not certain that I’d like to know what’s there, but the water is clear enough any day of the year to see the gravel on the bottom, which is much cleaner than the ponds I swam in when I was a kid. In early spring there will often be a bit of string algae, but the addition of a barley concentrate stops it from growing, and after it’s removed once by hand I don’t have enough regrowth to worry about.

The skimmer box protects the pump from clogging with a foam filter pad and a leaf net. These are cleaned a couple times a year by dumping the little bit of debris that accumulates in the net, and by hosing off the filter pad.

Since the pond is surrounded by towering trees I cover it with a large nylon net by the middle of October each year. The net is supported by cables to keep it from sagging too far into the pond. By mid-March the net is removed and the soggy leaves dumped in the compost pile. I remove the cables and cut back the spent foliage of the iris and cattails, but that’s it for spring cleanup.

The spring cleanup takes about an hour and a half, and that’s about the only labor spent on maintenance for the year besides a few minutes here and there. There are no chemicals used in the pond besides the barley concentrate, and the water in the swimming pond has never been emptied and refilled, though a few times a year when rain doesn’t keep up with evaporation I add some water.

When purchasing the components to build the pond I bought a large UV light, which was intended to assure the quality of the water, but at the last moment I discovered that I’d have to do more electrical work to install it, so the entire apparatus sits on a shelf in the garage. Also, I had intended to use an external pump rather than a submersible, but changed my mind, and have used the same pump without a problem. I’ve had pumps in the small ponds that have lasted ten years and longer, and I don’t see any reason why this one won’t.

Fish

None of the resources I consulted recommended having fish in a pond that you swim in, and I suppose the reasons are obvious, but I wanted to swim with the fish, so that seemed to be reason enough to ignore the recommendations. I was happy with my decision from the start, and am overjoyed after four years to have fish, and have never had a reason to think otherwise. I began with a dozen small koi, but as nature takes its course, a dozen became thirty, and then fifty or seventy. Some day there will be too many, and then I’ll have to transfer some to the other ponds, but for now, whatever number there are, it’s perfect.

Sometimes I feed them, sometimes not, but they require no care at all, and they’re always excited to see me.

Wildlife

With ponds you have frogs (there is no choice in the matter), and with six ponds there are lots of them. The racket from spring peepers is loud enough some evenings that I must close the windows to sleep. Walk down any path in the garden and you’ll hear the splashing of frogs into the stream and ponds, though if you move gently you might approach within inches before they flee.

There’s an occasional garter snake, but they’re so shy that they’re no concern, even to my wife. In the more shallow ponds I’ve had problems in years past with garters poaching small fish, but that has not been a problem in the larger pond. Nor are herons a problem in the swimming pond, where they are not able to stand in the deeper water.

There are plenty of dragonflies that dart about and perch on the cattails, surveying their domain to snatch the stray mosquito. And there are a variety of water skimming bugs zig zagging across the surface, and I’m surprised that the koi pay them no attention, perhaps they have too little substance to be considered a meal.

I have seen groundhogs, chipmunks, and squirrels stop for a drink, and know that deer and fox, skunks and possum visit the garden. Birds stop to splash about in the shallow water above the waterfall, and will hop from rock to rock in the shallow filtration area (under the cover of the tall iris and cattails) for a drink.

There has been only one occasion where geese were found in the pond, and a few ducks once, but they must be more comfortable in the larger, nearby farm ponds, where they are numerous.

Plants

In the filtration area of the swimming pond I have planted variegated cattails, tall striped sweetflag, Japanese and yellow flag iris, and floating hearts directly into the small bluestone gravel. When the water and air temperatures warm in late spring I plant tropical cannas, elephant ears, and dwarf papyrus that grow huge in the shallow water.

The aquatic plants help to filter nutrients from the water, but my purpose is to naturalize the pond’s edge, so between boulders half submerged at the water’s edge I’ve planted colorful Japanese iris, rushes, and calla lilies. In the soil above the boulders that edge the pond large leafed hostas and hydrangeas, and winter jasmine tumble to blend the pond with the garden.

The deep part of the pond is not planted, and floating hearts that wander from the filtration area are tugged out and tossed onto the compost pile.

Considerations

First, you should be aware that most communities consider any pond deeper than two feet to be a swimming pool, and permits and fences are normally required for safety.

Most pond building guides recommend against constructing near trees, where leaves will blow into the pond. I have no choice, my property is surrounded by trees, so I cover the ponds with netting in October that is removed in March. If the pond was fouled with leaves I’d be forced to empty the water to clean the mess in the spring, and I don’t intend to ever have to pump out the pond’s twenty-five thousand gallons and refill it.

The swimming pond in my garden is halfway to the back property line, so that you must follow paths past three smaller ponds, and cross a small lawn area to reach it. The pond (and the plantings that surround it) brings the upper and lower portions of the rear garden together, so that it is perfectly located, but in most situations the pond will be appreciated more if it is closer to the house.

When I first built the swimming pond I included a stone patio and firepit, and the following year added a metal summerhouse and another small patio. The planting area around the pond has been added to continually, and I’m certain that part of the project will never end.

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