During the winter months, Zack Herlick's koi fish slowly mill around near the bottom of his ponds. Bald cypress trees stand tall, sprouting from a pile of rocks submerged in the water. At their feet, water lilies and cannas add a soft green to the scene.
It's just a slower time of year for the fish and their habitat. Their metabolisms slow, putting them into what Herlick calls a light hibernation during the coolest parts of the year. This doesn't stop Herlick from sitting at the pond's edge, enjoying their calming company.
"As long as it doesn't freeze on the bottom, they are fine," he says. "They are hardy fish."
Herlick hasn't always known this, but has rather gleaned it during years of research and experience. As he has a background in finance, the world of koi fish and their habitats was completely foreign to him just like the koi fish themselves when he and his family moved into their Woodside home in 2006. Their new home in the countryside came with two koi/garden ponds: a 2,000-gallon, more traditional pond in the backyard and a shallow, 10,000-gallon pond just down the slope from their front door.
Today, almost 10 years into his koi hobby, Herlick is a certified koi health adviser through the Associated Koi Clubs of America program. This role allows him to help other koi keepers avoid the trials and errors that can come with raising koi fish.
"This is a very vulnerable time for the fish," Herlick says, speaking of the coming transition from winter to spring.
That's because pathogens can be waking up, like much of the budding world around them, but the fish could still be in a "light hibernation" when the temperatures are between 47 and 62, he says. To keep this problem at bay, Herlick urges koi pond owners to invest time in cleaning their ponds, like he will do. This includes cutting back plants, cleaning filters and routinely checking the water's pH, ammonia and nitrite levels. In addition, owners shouldn't be overfeeding their fish. Herlick says the grazing fish need little to no food in the cold months.
"In this area," he says, "I won't feed through the winter until about April."
As a general guide, he keeps to a feeding schedule that depends on the temperature:
• below 50 degrees: never feed.
• 50-60 degrees: rarely feed.
• 60-70 degrees: start feeding.
• above 70 degrees: feed frequently.
"Only give them what they can consume in the first couple of minutes," he says.
After those few minutes, koi keepers should skim away any excess, he says. If it isn't collected, it will build up on the sides and bottom of the pond, creating a bacteria-rich environment that can be harmful to the fish. This is especially important for Herlick because his ponds aren't traditional koi ponds, but instead hybrid koi and garden ponds, with sloped sides and plants submerged in the water.
In contrast, traditional koi ponds have straight sides. The edges help keep the pond clean and in turn the fish healthy. Dan Rutledge, co-owner of a koi pond and aquatic landscape company called Pond Life, says Japanese breeders don't use any plants or rocks in their ponds. He says many locals still want the plants and visual elements, so he works to create ponds that give the illusion of plants in the water but avoid problems such as introducing parasites to the water.
He got his start in koi back in the late 1970s, keeping his own koi and joining local koi associations, such as the Santa Clara Valley Koi & Water Garden Club. And then in 2004, he officially started building ponds.
"I want to help people create a pond that allows the koi to grow and is a well-balanced pond," he says.
When considering a pond, Rutledge said space and time commitment drive the design decisions. A traditional koi pond ranges from 5,000 to 6,000 gallons and sinks into the ground at least 3 1/2 feet. The depth keeps the water temperature more consistent and warmer on the bottom, he says. Plus, the depth deters predators such as herons because they can't stand in water of that depth. Owners can also add nets above the pond to keep predators out, but Rutledge avoids that option when he can.
"There is no such thing as a predator-proof pond," he says. "My preference is to not have to net the pond, so you can appreciate it."
Beyond the hole in the ground, pond builders have to consider their material, which can range from concrete and a rubber liner to fiberglass or a compound called gunite. Rutledge prefers the gunite option because it is less likely to leak and doesn't have folds, which can trap bacteria, like a rubber liner does.
Next, pond owners have to consider their level of maintenance commitment.
"There is no such thing as a maintenance free pond," he says, "but there are systems today that are very close to none."
Rutledge says there are filters on the market for just about any need.
"I want to match the system to the client," he says. "I don't want them to be disgusted with it in a few years and want to get rid of it."
Especially because he takes care of koi fish and builds ponds for their stress relieving not inducing characteristics.
"Water features are one of the most relaxing things you can have on your property," Rutledge says. "There is nothing like watching the colors of the koi as they swim around. The Japanese call them living jewels, and it is the truth. They are just like living jewels. It's very relaxing."
This article appeared in print in the Winter Home + Garden Design 2016 publication.