Most pond fish, such as koi, will eat insects and larvae on the water's surface. With proper planning and maintenance, a fishpond can actually reduce the number of pests in your garden.
Shahla Butler, whose vegetable garden we featured in our Summer 2011 issue, has two types of fishponds – koi and pond fish. “Our koi pond was constructed like a swimming pool with concrete sides. It is eight feet wide and six feet deep. With that much water you have to have good construction. Our three other fishponds are eighteen inches deep, simply lined with pond liners and stocked with smaller fish.”
When considering koi, it’s important to ensure that they will have ample oxygen. Even through the winter months, you should place a low-volume pump in the pond so it doesn’t completely freeze over. The easy part of winter care for koi is that they don’t need to be fed when they hibernate.
Butler adds, “From April to October, koi are voracious eaters. Koi food can be found in most garden centers. They also enjoy regular lettuce tossed into the pool. I don’t put plants in the koi pond because of the depth of the water. But sometimes I add some floating plants to give them something else to eat.”
Another big consideration with a koi pond is maintenance of a neutral pH. Natural debris from either trees or fish excrement can drive the pH up and acidify the water. When that happens, it’s time for a cleaning.
Butler says, “We thoroughly clean our pond about every three or four years. You don’t need a special oxygenated pond to transfer the koi to; it’s usually just a few hours that they’re in that temporary pond. We shovel out the bottom, hose it down, drain, fill again, check the pH, and we’re done. We use the pond scum for fertilizing tea we apply to the garden.”
Butler’s other fish ponds house water plants in plastic containers that are submerged and placed on top of concrete blocks. The holes in the blocks provide hiding places from the fish’s number-one predator, the heron.
Steve Garner of Garner Exteriors deals with the heron problem by placing black, see-through netting over his two-and-a-half-foot-deep koi pond. The pond is fed by bio-falls that spill over stone ledges and rocks, oxygenating the water. “I also installed a skimmer off to the side of the pond for algae control. The pump draws the filtered water back up to the top again. For easy maintenance, I also installed an auto-fill water supply to correct evaporation,” Garner explains.
Garner drains his water feature once a year, then power sprays the rocks, clean the filters and refills. During the summer he cleans the filter and skimmer box twice a month, a five-minute maintenance task. Every two or three years he replaces the filters. Chemicals are added on occasion to offset bacteria and algae, and oxygen depletion.
A fishpond is not only an aesthetic feature in any garden, but also a pest control bonus and an ecosystem for other water-loving critters, such as frogs. Hopefully it becomes a serious consideration for your next garden project. ✦
• Garden centers sell water pH and oxygen testing kits, as well as the chemicals to adjust your pond.
• Koi cost $2.00 to $2,000.
• Don’t place anything for a heron to stand on in the middle of your pond.
• Place your pond near a water and electric supply.
• The location should be not too shady and not in the full sun; also NOT a low spot.
• Other pond fish over four inches can be placed with koi.
• If stones are used in your pond, choose smooth stones so as not to puncture the liner.
• Create hiding places from the sun or a predator.
• Koi grow in relation to the size of your pond.