PONDS, PUMPS AND WATER PLANTS
Ideas and Tips

Q: What do I do about algae in ponds? Read tips.
Q: What size pump do I need? Read tips.
Q: How do I calculate pond volume? Read tips.
Q: What should I do for Fall Pond Care? Read tips.
Q: What about Natural Filtration? Read tips.

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Q: What do I do about algae in ponds?
A: There are several things you can do to reduce or eliminate algae in ponds. Pond plants can compete with algae for sunlight and nutrients. Keeping your pond clean is important. If algae starts growing, try the following:

• Check your filtration system. Make sure it is adequate.
• Add an ultraviolet clarifier (for green water).
• Use enzymatic cleaners: Pondzyme or Microbial Algae Clean.
• Use an algaecide.

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Q: What size pump do I need?
A: Generally speaking, at least 1/2 the volume of pond water should move each hour (so a 200 gallon pond needs at least a 100 gph pump). Waterfalls require 100-200 gph for every inch of spillway width.

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Q: How do I calculate pond volume?
A: You need to know your pond volume to determine the right pump, filter, water treatment, fish capacity, etc. To calculate your pond volume, the formula is : Surface Area X Average Depth X 7.5 = gallons of water.

Your Average Depth can easily be measured. Your surface area depends on the shape of your pond:

For a rectangle - Surface Area equals length times width.

For example, a rectangular 6' X 4' X 2' pond has a surface area of 24 sq ft (4' X 6'), an average depth of 2 feet, and a volume of 24 X 2 X 7.5 = 360 gallons.

For a circle: Measure the widest distance across. 1/2 of that is the radius, R. The surface area equals R X R X 3.14.

For example, if your circular pond is 5 feet wide and 2 feet deep, the surface area is 2.5 X 2.5 X 3.14 = 19.63, and the volume is 19.63 X 2 X 7.5 = 294.45 gallons.

For an oval: measure from the center to the farthest point (A) and the widest point (B). The surface area is A X B X 3.14.

For example, if the distances from the center are 3 feet and 2 feet and the pond is 2 feet deep, the surface area is 3 X 2 X 3.14 = 18.84, and the volume is 18.84 X 2 X 7.5 = 282.6 gallons. (Notice that the overall length and width are 6' X 4', but the volume is not the same as for the rectangular 6' X 4' X 2' pond.)

For a kidney-shaped pond: measure the longest point and the widest point of EACH end. The surface area is about 0.45 X length X (the two widths added together). So if your pond is 6 feet long, one side is 3.5 feet wide and the other 4.5 feet, and the depth is 2 feet, the surface area is 0.45 X 6 X (3.5 + 4.5) = 0.45 X 6 X 8 = 21.6 and the volume is 21.6 X 2 X 7.5 = 324 gallons.

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Q: What should I do for Fall Pond Care?

Are you paying attention to your pond this fall? Now is the time to watch for falling leaves and falling temperatures. Make sure that you remove dead foliage from hardy plants and that you skim off fallen leaves regularly. If you have lots of deciduous trees nearby, consider netting the whole pond until the majority of leaves have fallen. Pull water lettuce and hyacinths as they decline and compost them. This goes for fairy moss and duckweed as well. As they begin to darken, remove excess plants. Trust me, you only need to leave a little for next year.

October is also the time to pull tropical plants and either compost them or bring them in to overwinter. Many things such as papyrus, taro, and umbrella plants can be overwintered as houseplants. Lotus and tropical lilies can be lifted and stored as tubers. If your pond is at least 2-2 ½’ deep, you can also overwinter them on the bottom.

As temperatures drop, start feeding your fish a high carbohydrate, low protein food. Feed several small feedings a day, rather than once or twice. When water temperature falls below 60°F, decrease their feeding until you shut food off entirely somewhere around 50°F.

If you are unsure of what you need or how to take care of your pond for the fall, call or come into Sky. We look forward to helping you with your fall water gardening questions.

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Q: What about Natural Filtration?

One of the easiest and most attractive ways to filter your fishpond is with a bog filter. The advantages of bogs are many. They allow a more natural transition from land to water. They solve the problem of fish grazing plants. Most importantly, they can completely process both organic and inorganic waste. Bog filters can support a broad spectrum of plants and also create more habitat for creatures such as frogs, salamanders, and birds. A bog filter is truly nature’s filter.

The size of your bog filter will depend on the organic load you expect it to process. Generally a bog filter will be 10% of the surface area of your main pond; for heavy loads, go up to 20%.

Excavate an area that size next to your main pond to a depth of at least 12”. Build a concrete (or concrete block) retaining wall separating this area from the main wall. The top of the wall should be 1-2” below the pond surface when filled. Make the liner for the bog filter level; be sure to allow extra liner for the side of the retaining wall. Use felt protection mat or scrap liner to protect the liner from rough or sharp edges. Place liner in pond and bog filter according to vendor’s instructions.

(Alternatively, build the bog filter as an extra-wide 12” deep shelf, place the liner on it, and build the separating wall on TOP of the liner. Fill in any large cracks that would leak gravel with mortar or black expanding foam. Do not fill in cracks that are shallower than 2” below the pond surface.)

Install the pump in the main pond as far from the bog filter as possible. For ponds under 4,000 gallons use a pump which will circulate the pond volume at least once every two hours; for ponds over 4,000 gallons, circulate once every four hours. Screen or pre-filter the pump to prevent clogging. A full size filter is unnecessary.

Use oversized PVC pipe to build a distribution manifold the length of the bog; the pipe connecting to the pump should also be oversized. (For example, if the pump has a 1” outlet, use 2” pipe). To make the manifold, drill ¼” holes every 3” about halfway between the side and bottom of the pipe. Cap the far end of the pipe. Lay it on the bottom of the bog as far from the main pond as possible. (If the bog is wider than 3’, multiple lines are desirable.)

Place decorative (usually flat) rock across the top of the retaining wall, allowing small cracks between and under rocks for water flow. Water will be pumped from the main pond into the bog filter, filter through the gravel, and flow back into the pond over the retaining wall through the cracks.

Fill the bog filter with pea gravel, mounding the pea gravel so it is 3” ABOVE the water level for most of the bog. Mix larger river rock into the top layer of gravel for a more natural look. Incorporate rock from around the pond and landscape in the bog filter to visually tie the landscaping together, or use logs and other wood pieces if that’s appropriate.

Finally, plant up your new bog with marginals and other moisture-loving plants. Plant directly into the pea gravel. Bacteria that will break down any wastes in the water will colonize the pea gravel, the plants will use the nutrients to grow, and your new bog filter will return naturally clean water to your pond.

Instructions on creating the bog taken from an article by Jim Purcell, Jim’s Water Gardening, Eugene, OR. Used by permission.

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