How To Maintain A Healthy Pond
By Peter V. Fossel
It might be pushing things to call our farm pond a "pond," because you can't actually see much water in summer. What you see instead is algae, weeds, and bullfrog eyes.
"You don't have a pond, you have a wetland," says Fred Snyder, district specialist with the Ohio State University extension service, "and if that works for you, you're in business."
It doesn't work for many people, however, so Snyder's services are highly sought after by those who want their ponds "fixed."
"The main problems ponds have are too many weeds, too much algae, and not enough oxygen in summertime," he says. Depleted oxygen causes fish to die.
To keep a pond healthy, you've got to do several things, he says. The first is to reduce weed growth by eliminating nutrient sources such as lawn or farm fertilizer, livestock manure, or septic tank leachate (liquid produced by water trickling through the waste).
"Pond weeds are a natural process, but we speed it up with fertilizer runoff," he explains.
"Autumn leaves are a double-whammy if you have trees around the pond," he says. Falling leaves contain 60 percent of the nutrients a tree takes in during a year, he explains, so those nutrients now feed pond vegetation. In decomposing, leaves also take up dissolved oxygen, thus competing with fish for the oxygen supply. This results in more nutrients to feed even more pond weeds.
"It's a natural ecosystem," Snyder says. "Mother Nature wants plants in a pond. People don't. There's been a change in our mindset since the days of bullfrogs on lily pads. Now people want ponds to be like a swimming pool, with crystal clear water full of 5-pound bass. But you can't have both."
To eliminate the shallow water where weeds thrive, a pond should have relatively steep sides and good depth. A good slope is 1 foot down to every 3 feet across, and Snyder recommends that 25 percent of the pond be more than 8 feet deep - both for fish habitat and weed reduction.
Oxygen depletion causes fish kills in summer because oxygen is less soluble in warm water, which is exactly when fish are most active and need more oxygen.
"Learn to spot the problem," Snyder says, "because if it's serious, it's immediate, and you have to act. You don't have time to price-shop for an aerator."