Most experts agree on the effectiveness of ultraviolet filtration, but they vary on placement in clients’ ponds.
By Lisa Armony
Industry professionals laud ultraviolet filtration as a powerful tool in the fight against green water, especially in ponds where water clarity is challenged by common problems such as imbalanced ecosystems or filters that are too small for the size of the pond.
Typically used in residential pond applications as a water clarifier, UV filtration occurs when suspended algae cells pass by an ultraviolet bulb for sufficient time for a polar charge to occur. The UV causes algae cells to stick together and get trapped in the filter, according to Ben Plonski, president of Matala USA in Laguna Beach, Calif. Plonski said he considers UV to be standard equipment, particularly in ponds with rocks and gravel where bacteria can grow and in those with heavy fish loads.
"In general, UV is very helpful and alleviates a lot of frustration," Plonski said. "Natural garden ponds should have a light fish load. The more fish you have, the more food and fish waste there is and the easier it is for algae to grow. UV for these ponds is a definite requirement."
Because UV filters can include clarifying and sterilizing functions, usually within the same unit, Plonski said he advises contractors and retailers to be clear with their customers about what their UV systems will be used for. Clarifiers give clear water while sterilizers kill off bacteria and parasites for disease control.
According to Plonski, owners can achieve the less powerful clarifying function with 10 watts per 1,000 gallons and a minimum turnover rate of every two hours, depending on the fish load, the filter size and the amount of sun a pond gets. He has seen sterilizing performed with as much as 1 watt per gallon and an hourly turnover rate, which he said is not economically feasible for a residential pond.
Experts said equipment cost, which can run from $150 to $1,000 for larger ponds, deterred pond owners from buying UV systems in the past. Chris Thier, national sales manager at Laguna Water Gardening in Mansfield, Mass., said the clarity they give and their ease of maintenance make UV systems well worth the initial expense.
"Once pond owners understand what UV is used for and can overcome the initial cost, they get into a 'set it and forget it' mentality," Thier said. "They can set up the UV with the proper flow rate, and it takes care of the problem. If you add beneficial bacteria, you have to do that every week or every couple of weeks. If you hook up the UV properly, you won't have to deal with it for the entire season."
Pond owners with UV filtration still might need to add beneficial bacteria for string algae or sludge, but the number of treatments needed in UV-installed ponds is reduced greatly, making it a better up-front expense, Thier said. While many experts agree on UV effectiveness, contractors and retailers reported different approaches when it comes to installing them in their clients’ ponds.
Arnie Pellegrino, owner of Long Island Elite Landscape Construction in Long Island, N.Y., said he recommends UV filters to all of his customers.
"My goal is to let Mother Nature work with your system, so I suggest first a skimmer, then a UV light and then a filter," Pellegrino said. "The filter is not as important as the UV light. I recommend putting on a good UV light with a good pump and a skimmer to catch leaves and housing for the pump so there's easy access. You can draw water through a skimmer or bog so it circulates. Once you do that, you have it pass the UV light and go back into the pond. That should cover most of your issues."
When customers report problems with green water, Jeff Kite, vice president of sales for Sunland Water Gardens in Sunland, Calif., said he walks them through a checklist of possible causes before recommending UV.
"We start by asking about their filtration - what kind they have, when was the last time they cleaned it and how often do they clean it," Kite said. "We go through the basics first and try to figure out all the problems without UV. Once we get to the point where we see that the filter is clean, running 24 hours a day, has time to balance out and they're still not getting clarity and they don't want to use clarifiers and algae-control products, we tell them that UV is the next step and that it solves the problem 90 percent of the time. That's when people usually decide to go with UV."
Greg Leston, president of Creative Water Gardens in Lombard, Ill., said UV's inability to kill algae spores or string algae makes it ineffective for clarifying residential ponds.
"Only 1 to 2 percent of people have suspended algae problems where UV would be effective," Leston said. "Most have string algae, so it's not effective. Algae blooms are caused by something really being out of balance, like inadequate oxygenation, a high nutrient load or overpopulation. Green water usually is temporary, like maybe phosphate got into the pond from fertilizer. Change that and the problem goes away."
Although Leston does not recommend UV to his clients, he uses UV as a sterilizer in his hospital tank where he uses a 600-watt UV bulb housed in a 36-inch-long stainless steel reflective chamber with a very slow flow rate. That set-up is impractical for most residential ponds though, he said.
Some retailers and manufacturers report growing consumer interest in residential UV use. Kite said about 40 percent of his customers already have installed UV, and he expects more to do so as they become aware of its benefits.
With the recession continuing to take its toll on consumer spending, Scott Paparella, marketing manager for Emperor Aquatics Inc. in Pottstown, Pa., reported growing sales of single units that perform mechanical, biological and UV filtration. Once a cause of concern due to fear that combined filters would kill off beneficial bacteria, Paparella said these systems prove very efficient and do not pose a danger to the bacteria needed to keep ponds in balance.
"With our system, the majority of bacteria cling to the walls and filter and are safe from the UV, which is located at the back of the filter," Paparella said. "The units are easy to install and consumers can even install them themselves if they have the right information.”
Kite said the pond size often determines whether to go with single or separate units.
"We sell the all-in-one units and people do like these," Kite said. "With larger ponds, we install UVs that are in line with their other equipment. A lot of people have external pumps so they go in line with their existing filtration and that keeps the green water away.”