Are your fish and plants ready for cold weather?

Introduction

Right now, most of us are getting ready for fall by pulling up faded annuals, mulching perennial beds and raking leaves. Autumn clean-up comes almost instinctively to seasoned gardeners. But what about the water garden? Is your pond ready for winter? Even the most successful water gardeners sometimes wonder if the pond will "make it " through the winter. Stop worrying. Let's look at the steps necessary to over-winter the pond and discuss how it relates to a beautiful water garden next spring.

Why can't I just let nature take care of my pond?

All summer long, you've enjoyed the tranquility of the water garden-beautiful foliage, sounds of trickling water and colorful fish eagerly awaiting a handful of food. The water garden didn't get that way by itself. You added the right kinds of plants and fish to create a balanced ecosystem. The water gardens we create look beautiful and sustain life because we follow nature's rules. It's the same during the winter months. Despite all outward appearances, the pond is active even when the water is cold or even frozen. Dead leaves, algae, insects and solid fish waste that have accumulated over the summer slowly break down during the winter months. This natural decomposition uses oxygen and produces small amounts of hydrogen sulfide, a toxic gas that normally never reaches a harmful level. Few water gardeners realize that the pond must be balanced in winter too. Fish, frogs and other aquatic life are especially sensitive to poor water quality in winter. A build-up of leaves and other organic matter can cause an imbalance, reducing oxygen to dangerously low levels and releasing poisonous hydrogen sulfide. One autumn I decided to see how well nature would take care of my two ponds. I let the lily leaves die back naturally, falling into the pond. Leaves and sludge covered the bottom of the pond. What could go wrong? It looked natural. Come next spring when the ice melted, I was shoveling out black, stinky ooze garnished with dead snails, frogs and my prized fish. I learned my lesson well. Now I use a coarse net to remove dead leaves. I also use a fine weave aquarium net to remove sludge. You can reduce sludge build-up with bacterial "cleaning" products for water gardens. These products contain bacteria that digest dead algae, plants and sludge that accumulate in filters and at the bottom of the pond. Bacterial products are completely safe and help keep water gardens clean. While your stirring things up, why not change some of the water? Algae promoting nutrients, dissolved organic matter and natural acids build up in all water gardens. These substances can stress pond life and lower oxygen and pH levels. Partial water changes flush out these substances and improve water quality. I change 50 % of the water in my ponds in autumn. If a pond has a lot of suspended matter or the water is tinted yellow from dissolved organics, I'll make two water changes a day apart. While I'm pumping out the water, I stir up the sludge. Pump out the sludge and old water at the same time! Remember to add Stress Coat to the pond before refilling it with tap water. Stress Coat will condition the water and add a protective slime coat for the fish

Too much of a good thing

This may seem contradictory, but you want to leave a little bit of debris in the pond when preparing it for winter. Some water gardeners net out the fish, completely drain the water and scrub out the pond, refilling it with fresh water. Frogs, tadpoles, snails and microscopic pond life need to burrow down into mud and leaves to survive the winter. Fish also hibernate on the bottom, settling in around a bed of leaves and mud. I remove about 90% of the leaves and silt that have accumulated over the summer. Leave the rest as "bedding material." You'll be amazed at the diversity of pond life that emerges in spring. Keep in mind that tree leaves will continually blow into the pond as long as the water isn't frozen. I recommend covering the pond with bird netting. This black plastic netting is almost invisible and prevents tree leaves and debris from getting into the pond.

Pumps and filters

You won't need to filter the water but it's a good idea to keep it moving at the pond's surface. Pond life needs oxygen even during hibernation. If ice covers the surface of the pond, oxygen can't get in and toxic gasses can't get out. Submerged pumps with fountains or waterfalls will oxygenate the water and keep a portion of the pond from freezing. If you live in an area that freezes solid I recommend using a pump and fountain to aerate the water. Set the pump on bricks about one foot below the water. This will prevent the pump from getting clogged with leaves. If your fountain output appears to be diminishing, check the pump to make sure it is not clogged. Floating pond heaters are available to keep a small area free of ice. You can also use an aquarium air pump and diffuser stone to oxygenate and prevent ice formation. Even if the pond completely freezes over, the air pump keeps pumping oxygen into the water.

Over-wintering pond fish

The metabolism of koi and goldfish is controlled primarily by water temperature. As the water cools, pond fish require less protein in their diet. When koi and goldfish are fed high-protein food in cool water, the excess protein is excreted as ammonia from the gills. The microscopic organisms that make up the biological filter (and consume ammonia) also slow down in cooler water. Improper seasonal feeding can lead to a build-up of toxic ammonia, which stresses fish and reduces their winter survivability. When the water temperature drops to approximately 65° F, start feeding with Spring & Autumn Pond Food. This type of fish food is better suited for the dietary requirements of pond fish in cool water and won't pollute the water with excess ammonia. Some water gardeners continue to feed their fish until they no longer come to the surface. I stop feeding my pond fish when the water falls below 42° F.

There is no need to worry about "frozen fish" if a section of the pond is at least 18 inches deep. Pond fish will seek the deepest part of the pond and over-winter there until the water warms in the spring. If your pond is less than 18 inches deep, the fish may freeze during a harsh winter. Check with your local pond supplier if you live in an area with harsh winters. Water gardeners with shallow ponds can keep their koi and goldfish in kiddie pools or aquariums set up in a cool basement or garage. All that is required is an aquarium air pump or small fountain to provide oxygenation. The fish are fed infrequently, if at all, depending on the water temperature. pH, ammonia and nitrite should be monitored weekly, especially if the fish are fed. Small water changes (20%) each month will keep the water in good shape until spring. Koi are "jumpers"-so be sure to cover the pool with bird netting!

Caring for aquatic plants

Long after the impatiens have been pulled out, water gardeners are still hoping for that last lily bloom. For some reason, we want to squeeze every leaf, bud and blossom out of our aquatic plants before winter. Unfortunately, cold weather often comes before we've trimmed the cattails or pruned the lilies. Wait too long and all those beautiful leaves will fall off and rot in the water. Trim bog and marsh plants such as papyrus, taro and cattails, before frost hits. Pull out the hardy water lilies and trim off all the leaves. Yes, even that last bud! Put all the potted plants into the deepest area of the pond to prevent freeze damage. Tropical lilies won't survive the winter and are often treated as annuals, discarded in autumn. Some water gardeners have saved tropical lilies by storing them in peat moss. Trim off the leaves and roots and cover the rhizomes in a tray of damp (not wet) peat moss. The peat moss has antiseptic properties and helps inhibit rotting of the rhizome. The tray of peat moss should be kept in a cool basement or garage and sprayed with water periodically to prevent drying out. Inexpensive submerged plants, such as Elodea and Cabomba should be discarded.

Winter's rest

The transition of summer to autumn does not mark the death of the water garden. It's simply a time of rest for aquatic life. With proper care, the fish, hardy plants and tiny organisms that balanced your pond in the summer can survive the winter. Much of this care is simply an adaptation of the pond maintenance you've been practicing throughout the summer. Don't wait for winter-get the pond ready now! You'll have healthier fish, hardier plants and clearer water in the spring.