Aging PondHow a Pond Ages

By Bob Lusk

Like a proud parent, you stand on top of the dam of your new pond. There it is, in all its brand new glory, the smell of fresh earth recently shifted, molded and packed into what will soon be a bustling new environment of underwater mystery. You can’t wait to stock it with your favorite fish and then watch as Nature does her magic with the food chain and plants and wildlife. It’s an exciting time.

Or, maybe you are standing next to a pond that’s been around for eon’s, scratching your head over some new facts you’ve just learned. The old timers who were around when the pond was built say that it is 22 feet deep. You’ve come to the realization that the deepest water is 14 feet. What gives?

From the moment a pond is impounded, it begins to age. Freshly moved earth commingles with dirt that’s been in place for years. When it rains, water moves the smaller particles, creating new little cuts and crevices.

The dirt which moves with the running water heads follows the path of least resistance…as close to the bottom of your pond as it can get.

More rains follow and more small particles move deeper, forming little underwater deltas in your new pond.

Over years and years, ponds continue this process, from whatever nearby sources it can. This process is called “siltation”. Silt, mostly the smallest of dirt particles, finds its way into your pond until surrounding soils can grow enough greenery to prevent it.

Then, the plants contribute. Leaves in the fall, grass clippings, underwater vegetation as it dies and sinks…all these processes contribute to the aging of your pond. As organic matter settles to the bottom, it slowly decomposes and mixes with the soils. Organic matter needs oxygen to properly decompose, but under water, oxygen is limited. So, organic matter often takes a long time to decompose and break down to its fundamental elements. Even if it does, new plants want to use this compost to assist their life cycles.

Is there an anti-wrinkle cream for aging ponds?

Yes, there is.

Move the water, via aeration. The more the water moves, the more it’s able to do what it does, break down organic matter into its fundamental elements so Nature can use them again, or dispose of them via flushing when the next rains come.

As a pond ages, it matures. The fishery matures, the plants grow and the pond slowly fills in. Given enough time, a pond will go from its early life of plentiful, deep water to a shallow hole, to an expanding marsh to a wetland to dry land.

In today’s pond management world, aeration helps postpone some of this fate, especially when it comes to the organic matter.

What about that silt, you might ask?

Be sure your earthmover adds a healthy layer of topsoil to the areas which won’t be flooded. Then, vegetate those areas as soon as you can. Don’t wait. Find out what the best grasses or ground cover is best suited to your area and get it done. The sooner you can vegetate freshly moved dirt, the better. That prevents siltation…or at least minimizes it.

Aeration? What’s that?

There are a variety of products on the market. If you don’t have electricity near the pond, consider wind-driven aeration or a solar powered unit.

If you have electricity, you have a variety of choices. There are circulators, fountains, bottom-diffuser systems. Do your homework, based on your goals. If you want to zero in on siltation and reduce build-up of organic matter, a bottom-diffuser is a good choice. These systems push high volumes of low pressure air through a hose on the bottom of your pond into a diffuser which breaks the air into zillions of tiny bubbles which cascade from the bottom up. A bubble plume makes its way to the surface and carries lots and lots of water with it. As the water moves vertically, loose soils at the bottom are moved, too. As air mixes with water at the surface interface with the atmosphere, the water expels gasses and helps facilitate the breakdown of the organic matter trapped on the bottom.

Careful, though. Don’t get into a hurry with this exciting biology stuff. If you buy and install an aeration system for your existing pond, be careful how you use it. Don’t expect to undo what it took Nature years to cause. If you turn on an aeration system and let it run too long in a pond that has a few years under its belt, expect it to rebel. All that nastiness on the bottom, if shifted too quickly to the top, will get the last laugh…and kill your precious fish at the same time. Do it slowly, an hour each day to start. Then, bump it up a notch. After the aeration system does its work and gets that area of underwater junk to break down over a week or two, then leave the system on full time.

Not only will an aeration system assist with the breakdown of organic matter, it will be a good insurance policy against water quality that tends to breakdown during the hottest months. Water chemistry and biology tends to stabilize in the presence of aeration.

As you learn about the best methods to manage your favorite fishing hole, or that pristine-looking pond in its pastoral setting you can see from the porch, remember that it ages because it slowly fills with Nature’s traveling sediment band. That’s not the kind of music you might like to hear, so formulate a plan to prevent it with good practices at the start. Vegetate bare soils. Use aeration to expedite Nature’s offerings of organic matter. Catch big fish. Watch wildlife enjoy the pond. Drink a glass of your favorite summer beverage and smile…as your pond ages gracefully.