Clear Water

by Kit Knotts - Click images to enlarge

Pea soup may be fine in the kitchen but not in your pond! Having clear water is sometimes the greatest challenge that faces the water gardener. In most cases the answer is a simple one - leave the pond alone.

We believe that clear water is best achieved by allowing the pond to achieve natural balance. This means finding the proper combination of plants, fish, snails, beneficial bacteria and, believe it or not, algae. Expensive and/or complicated filtration isn't necessary.

Green water is the worst way a pond can be murky. This occurs when nutrients in the water exceed the plants available to utilize them, allowing single celled algae to thrive and turn the water green. This often happens in spring as the water warms. In a healthy pond, plant growth will soon catch up and the single celled algae will go away on their own.

In our view, the quickest way to establish the health of a new pond (or one recovering from winter) is to add dirt, debris from other ponds (even from the compost pile), fish, snails, and any plants available. We will even "transplant" mossy or rooted algae.

One of the first water gardening books we read contained the sentence, "Algae is your friend" or something like that. There are thousands of types of algae, some awful to look at, some annoying and some rather attractive. The mossy type that adheres to the sides of a healthy pond is very beneficial, as are the rooted types. The point is that you can choose what you want to inhabit your pond.

Dirt, sludge and silt (the combination sometimes called "mulm") on the bottom of the pond provide a home for beneficial bacteria necessary for overall pond balance. We never clean our ponds but, if it should be necessary, we would consider jump-starting the bacteria population with one of a number of multiple-bacteria products on the market for ponds.

As a rule of thumb, 40% of the water's surface should be covered with foliage of some kind in cooler months, increasing to 70% in the warm months. The foliage shades the water, keeping it cooler (discouraging algae) and the plants utilize some of the nutrients in the water (discouraging algae).

Encouraging plant growth discourages algae growth. Most aquatic plants require at least five hours of full sun to grow well, more sun whenever possible. Because algae is more adaptable, it can out-compete plants in a pond that is too shady. Plant selection for shade tolerance is a factor in this case if pruning to provide more sun is not possible.

Fertilizing plants will NOT promote algae growth, as many seem to think, if applied properly. Aquatic fertilizer tablets are designed to break down quickly once wet. It's important to place them well into the soil and cover the hole after doing so. This will prevent rapid escape of the nutrients into the water. The benefits of fertilizing regularly far outweigh the risks of creating more algae.

Probably the second least desirable algae to the single-celled type are string algae. Other than increasing plant coverage, there is no remedy for them except manual removal. They will go away when plant coverage is adequate for pond balance without them utilizing the excess nutrients.

Water hyacinths (if they are legal where you live) utilize nutrients and absorb heavy metals far better than any other pond plant. If used, they should be anchored to the side of the pond with string or wire. Even though they are floaters, they don't like to float around. Overgrowth is easily remedied by thinning but disposal must never be in an open waterway as they are extremely invasive.

Waterfalls and fountains are pleasant additions to many ponds but a pump placed on the pond bottom can keep sediment stirred up, making the water murky. Elevating the pump off the bottom will solve the problem in most cases.

Small native fish are the best choice for pond balance, are usually self-limiting in numbers and they reduce or eliminate mosquito development. Fancy fish can keep the sediment stirred up. They also contribute their waste to the nutrients available for algae growth. Limiting the fish population and feeding them little if any supplemental food (beyond what is available naturally in the pond) will help keep the nutrients at a manageable level.

Snails are the pond clean-up crew, eating decaying matter. Ramshorns are the best bet. Large decorative snails from the pet shop should be avoided as they do eat healthy foliage.

Soil selection for planting can also be a factor in water clarity. Top soil can turn the water black and clay can make it milky. Both will settle out in time but the discoloration will return any time the pond is disturbed. Placing a layer of plain sand or gravel over the soil will reduce its escape into the water.

and a new pond
in Paradise

The new pond in Paradise makes a perfect illustration of achieving pond balance naturally (and quickly). On the dune between Reflection and the Pods, "Stars" is the first of a three-pond complex. "Sun" and "Moon" will replace the temporary tank in the background and be home to Victoria seedlings and adults.

The picture above was taken Wednesday, April 29, 2004 prior to the pond's completion. We finished it Friday morning. By Friday afternoon, we put a thin layer of peat over the concrete and 4-6" of sand.

Because we used some city water in addition to well water to fill it, we waited until Saturday to begin putting things in it.

 We added native fish, ramshorn snails, Nitella (rooted algae), water hyacinths and "pickings" from other ponds. There is no pump, no filter, no skimmer, no UV sterilizer, only a slight trickle of well water to replace evaporation.
Sunday, May 2, 2004, the water was 76-87F and crystal clear.

We plan to do nothing else to the pond until we install its Victoria and will update these images weekly -- hopefully to show that the water will remain clear.

May 9, 2004
A white pipe stuck in the pond bottom illustrates the water clarity.

May 16, 2004
Water temperature 76-90F
The only addition this week has been some overflow Victoria seedlings.

May 23, 2004
A few more baby Victorias have found their way to Stars. The water is still clear.

 The Sustainable Pond by Jamie Vande

Solving The Green Water Blues
by members of our email discussion list

May 30, 2004
Water temperature 81-92
Water is clear.

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