Overpowering Pond Scum

Science project: Cut one 2-liter bottle in half and poke several holes around the open end of the bottle. Fill the bottle a quarter of the way with fish tank gravel and add the aquatic plants, water and a guppy or two. Next, soak a piece of string in water for several minutes, then tie a knot in the middle of the string. Poke a hole in the bottle cap and run the wet string through the hole until the knot catches. Holding the top half of the bottle upside down, fill it with soil and small, leafy plants. Set the top half of the bottle inside the bottom so the string dangles in the water, then seal the seam between the two bottles with the tape without blocking the holes that will let air into the bottom half.

Voila! You’ve just created an ecosystem. The fish in the lower half of the bottle will be able to breathe through the air holes and eat the aquatic plants. The water and nutrients from the fish waste will be pulled up through the string, which will water and fertilize the plants growing on top.

Alas, for many eighth graders, this fun experiment – which happens to recreate the ecosystems formed from well-designed landscape water features – often results in dead guppies. However, with the proper installation and maintenance techniques, landscape contractors can create healthy, sustainable environments in their clients’ backyard ponds, complete with colorful Koi and thriving aquatic plants.

WATERTIGHT INSIGHT. To create a low-maintenance pond, industry veterans recommend starting at the bottom – that is, with the proper pond liners and installation techniques. Liners are the first component to proper installation because, after excavating the pond site, liners hold the pond together and keep the water within its boundaries.

"You always need to use a rubber liner to make sure all the water pumped out of the pond gets back into the pond," notes Gary Wittstock, president, Pond Supplies of America, Yorkville, Ill. "We recommend using rubber liners referred to as EPDM that come in widths of 5 to 50 feet. Some people may use roofing liners, but those can contain contaminates that can be harmful in a pond with fish or plants."

Sheets of EPDM rubber, a high-performance material that withstands the elements, are often used in pond liners because they do not introduce contaminates into the pond environment and conform well to the plant shelves and sides of pond designs. Wittstock recommends using 45 mil liners, reporting that this weight is plenty sturdy for large and small ponds and that heavier liners are too stiff to mold to curvy pond edges.

After installing the liner, Wittstock suggests covering the liner’s surface with large rocks and stones, as well as some ¼- to 2-inch gravel to fill in the gaps. According to Wittstock, this bottom layer protects the liner from being punctured by bird and animal life and also provides nooks and crannies where beneficial bacteria can grow and help out later in the maintenance program.

Other contractors have different pond-lining preferences. For instance, Barry Fox, owner, Falls by Fox, Littleton, Colo., prefers to veneer stones to the liner using concrete, rather than simply letting stones sit on the liner. Likewise, Darren Lucas, owner, Nature’s Touch Ponds & Supplies, Paramus, N.J., uses concrete when he builds ponds on sandy soil because it strengthens the pond’s structure.

However, simply filling a pond base with a layer of concrete is not enough, Fox adds. "The concrete is strictly ornamental," he says. "Because it’s porous, concrete won’t hold water – you could have concrete 1 foot thick and water would still find its way through the air pockets and cause damage to the structure of the pond. With a liner underneath, the concrete just becomes a better way to make sure the rocks we use stay in place."

DON’T SKIM THIS SECTION. With a watertight pond construction in place, contractors can install the most important pond components to keep water features crystal clear: skimmers and filters.

"I see a lot of underfiltration in ponds that I restore," Lucas says. "If your filter isn’t strong enough and you have a lot of rocks there can be a huge anaerobic bacteria problem that can kill the fish."

Wittstock agrees. "Because contractors want to win their bids, they may go with the least expensive filter that will still work for the pond to keep the overall price down," he comments. "I’ve seen this in combination with using too large a pump that then overpowers the filter. Because the pump is pulling too much water through, the filter gets dirty too fast and the system needs more maintenance."

Wittstock’s rule of thumb is to use a pump that moves 10 times the surface area of the pond, per hour. For a 10-foot by 10-foot pond a 1,000-gallon-per-hour (gph) pump is the minimum size. He notes that waterfall size also will be dependent on the pump, yielding about a 1-foot-wide waterfall for every 1,000 gph. "If the customer wants a 3-foot-wide waterfall, they’ll need a 3,000 gph pump in order to push more water. There may be a bit more skimmer maintenance necessary, but this size pump is the most popular and provides the contractor with some flexibility because he can split up the waterfall streams into one that’s 1 foot wide and one that’s 2 feet wide, for example."

In addition to choosing the proper pump to pull water through the pond’s skimmer box and into the filters, the contractor must identify what type of filtration the pond needs. "It’s important to know whether your customer wants fish or not," Fox says. "Some customers never want fish, but the contractor will use the same filtration for fish ponds and non-fish ponds."

In a non-fish pond, Fox uses a high-pressure sand-based filter similar to those used in swimming pools. Ponds like these require only a chlorine tab once a week for maintenance, Fox says, since there is no animal life to worry about.

However, chlorine is harmful to fish, so for fish ponds, Wittstock recommends biological filters for purification and mechanical filtration via skimmers. Skimmers cost as little as $100 to $150 and remove leaves, insects and debris from the surface of the water. "A biological waterfall filtration system takes the water cleaned by the skimmer and moves it through a second set of filter pads," he explains. "From there you can include media, such as lava rocks that are very porous and have a lot of surface area where good bacteria can live, like the kind in a septic tank. As the water moves through the second series of filters, the waterfall ejects the clean water back into the pond."

Additionally, aquatic plants also provide a type of biological filtration that keeps ponds clean – especially when fish are involved.

"A key maintenance point on fish ponds is having an even balance between your fish and your plants," Fox says. "Most people will say that you should cover 60 percent of the surface of the pond with plants. I’m a little more lenient than that and usually suggest a minimum of 40 percent. This leaves the pond with an appropriate ratio of fish to plants, but doesn’t obscure as much of the pond’s surface."

Fox explains that a pond without the proper fish/plant ratio can easily turn green with algae and make for an uninviting water feature. "It’s the sun that creates algae, which feeds on nitrogen," he says. "If you block out a good portion of the sun with the plants, that’s the start of a healthy ecosystem. From there, the fish poop and the poop turns into nitrogen, which is absorbed by the plants. If the plants aren’t there to absorb the nitrogen, the algae will continue to grow because you’re essentially fertilizing it."

Another source of nitrogen is debris that sinks to the pond floor before it can be removed by the skimmer. To solve this problem, Lucas installs bottom drains in his ponds. "We use a bottom drain that collects all the debris and fish waste from the bottom of the pond and that’s gravity fed into a big filter system," he says. "It’s much easier to install these at the start of the project than to have to go in with a net and pull up everything that’s settled on the bottom." These effective products can range from $50 to $100.

With adequate filtration, contractors note that most fish ponds won’t require many chemicals to keep the water levels in line. Still, Wittstock and Lucas both note that adding beneficial bacteria to the water on about a monthly basis – about 1 teaspoon per 1000 gallons of water – helps with the natural, biological filtration of the pond. Also, Fox uses muriatic acid to bring down high pH levels back to the normal 7.5 to 8.

10-MINUTE DRILL. While the skimmers, filters and overall ecosystem in a pond seem to do all the necessary work to keep the pond fresh, contractors still must make at least monthly visits to check on water features and clean the cleaners. Unfortunately, some contractors have reputations of skipping this step. "Among homeowners, too many contractors have the image of disappearing after they finish installing a pond," says Don Schnoor, vice president, Aquatic Gardens & Koi Co., Jobstown, N.J.

What makes that comment so curious is the fact that maintenance for a properly installed pond is small, costing contractors time and money that can be easily recouped in maintenance sales. Most contractors note that they generally charge between $75 and $500 a month for maintenance of ponds starting at 5-feet-by-10-feet. "When we did pond installation and maintenance we were able to charge a base price of about $250 for ponds this size," Schnoor says, adding that offering complete maintenance services helps contractors appear professional to their clients. "A contractor should be able to make a good hourly rate by charging this much for a pond cleaning and they will also weed out customers who are not willing to spend money for maintenance services."

According to Schnoor and other pond maintenance professionals, monthly maintenance visits should include checking the pond’s pump to make sure the intake is not clogged in any way; cleaning out the filtration system and the skimmer; fertilizing and trimming aquatic plants as needed; and testing the water for pH, ammonia, nitrates, nitrites and salt levels. Contractors also should have on hand any chemicals necessary to adjust water quality.

Of all of these steps, cleaning the filter pads takes the most time – about five minutes. Lucas explains the easy process: "To clean the filter pads, you just need to shut off the flow to the filter temporarily and allow it to drain," he says. "From there, the technician can remove the skimmer bag and clean out any leaves and debris that have been trapped there and remove and hose down the filter pads to clean off any excess build up." Some manufacturers report that filter pads can hold as much as 4 pounds of dirt before cleaning is necessary, but that the pads should not be cleaned too often because they work better as they collect more debris.

Altogether, most pond maintenance takes only 10 or 15 minutes for each monthly visit. However, most contractors and manufacturers note that ponds may require maintenance as often as every week during the fall when trees drop their leaves and skimmers must work overtime. However, quick cleaning drills allow contractors to make numerous pond maintenance visits in a day. For full-service companies who install and maintain ponds, the work also may be left to regular lawn maintenance crews to handle on their weekly routes, creating a highly efficient maintenance service.

However, there are maintenance visits that take significantly more time. For instance, opening and closing a pond at the beginning and end of a season can take a couple of hours when done properly. "The fall is considered the best time of year to clean the pond because you need to make sure the pond is clear of debris before winter sets in," Schnoor says. Otherwise, decaying material that gets trapped beneath iced-over ponds can produce harmful gases and asphyxiate the fish. For this same reason, Fox adds that fish should not be fed during the winter months.

To clean the pond completely and close it for the season, Schnoor suggests the following steps:

1. Move the pond fish to 100-gallon holding tanks (see A Fishy Situation on page 168 for more information).

2. Remove all tropical plants and either discard or store them properly for the winter. Hardy plants should be cut back to the top of the pot and placed in the bottom of the pond before refilling it with water.

3. Move all pond debris to the lowest pond area and remove it with a large dustpan and brush or a pond vacuum.

4. Clean and winterize the filtration system as necessary.

5. Place hardy plants back in the bottom of the pond and refill the pond with water. If the water is from a city water source that contains chlorine, dechlorinator may be needed to neutralize the water for fish and plant safety.

6. Acclimate the fish to the new water temperature and replace them in the pond.

7. Place a pond net over the pond to catch any debris that may fall during the course of the winter.

Opening the pond again for the spring requires similar steps, though removing the fish and draining the pond completely may not be necessary if the pond was closed properly the previous winter. Schnoor notes that plants can be removed from the bottom of the pond and replaced into their proper locations for the season, and clients should be advised to begin feeding the fish again when the water reaches 45 to 50 degrees Fahrenheit.

While the plants and fish will be perfectly safe in a cold pond during the winter, contractors and manufacturers recommend that a small amount of pond surface area remain free of ice to allow for the exchange of gases. Fox’s clients keep their waterfalls running during the winter so ice stays broken up, though there are several other methods available.

"Rather than running the waterfall all winter, which can artificially chill the pond, some pond customers may choose to install a "tee" in their systems which would take the water from the skimmer box and put it directly back into the pond instead of routing it through the waterfall," Wittstock says. "This will still keep ice from forming in that area of the pond. Also, you can install a floating heater to keep the ice broken up, though a heater alone may be inadequate in ponds with many fish. A single small hole won’t exchange enough gas to keep the fish healthy."

And, of course, healthy fish are essential for strong ecosystems like landscape ponds. In order to keep water features like these robust and attractive, contractors must follow thorough monthly maintenance schedules. Taking just a few minutes a month and a couple hours a year to service clients’ ponds can help contractors keep these water features from becoming trial-and-error science experiments.

The author is associate editor of Lawn & Landscape magazine and can be reached at lspiers@lawnandlandscape.com.