Swimming Into Spring

Goldfish and koi hate wintertime more than we do. Neither species of fish are indigenous to North America, so here they merely "survive" winter. They don't flourish in it.

By Dr. Erik Johnson

My name is Dr. Erik Johnson and I am a fish veterinarian. My practice is located in Georgia, which typically has balmy winters and very little ice on the ponds. However, winter's effects on the fish seem to be the same whether the pond is merely icy, or iced over. This article intends to inform you of some wintertime facts, but more importantly, this article will seek to use those facts to guide you through a safe and healthy springtime.

Assessing Their Health
Direct examination is important but can be difficult during the wintertime when the fish are not feeding. So, if the fish are not congregating for food, or schooling around the pond, how can you assess their health?

You need to spend the time, on a regular basis, to look at the fish as they rest in the pond. Look for clamped fins, redness in the skin or fins, swollen eyes or lips, or fraying, rotting fins. Look for a single fish that is not resting with the other fish. Look for white slimy patches on the fish. All of these symptoms could indicate that the combination of winter's stress – no food, and possibly an opportunistic parasite – is working on the fish. I have seen cases where people put mirrors on the pond bottom. This way, as the fish swim over the mirror, they can examine the bellies of the fish.

Alleviating Winter Stress
We know that winter is a stressful time for fish. One way to alleviate some of that stress is to apply salt at a rate of three pounds per 100 U.S. gallons. Using aquarium or pond salt is recommended, but some folks use non-mineralized cattle salt, water softener salt, or rock salt. It's best not to use iodized salt, but if you do, it will not kill fish.

Salt in certain amounts will kill some or all of your plants. This is especially true for plants that cost a lot of money. If you spent anywhere close to $50 for a plant, or if it's rare, it will die, flat out, in salted water.

Coming Out of Winter Hibernation
Fish are cold-blooded creatures, or poikilotherms. They don't produce their own heat and so they have developed enzyme systems to provide them with bodily functions such as the production of energy, regardless of temperature. These enzymes are called isoenzymes. They are produced as needed and they work in colder conditions. As the water gradually warms up in the spring, these coldwater isoenzymes are no longer produced. This is when the regular enzyme systems begin to function.

Before the fish get "warm" in summer, there's a narrow period of time where the water temperatures are too cold for the fish immune system to function optimally, but parasitic and bacterial populations are proliferating at explosive rates. This is when the fish are most prone to developing illnesses.

Further compounding these difficulties, fish have usually not been fed all winter – so they have been in a catabolic energy balance (net loss of energy) instead of gain. Feeding koi in the springtime is important in rebuilding these energy stores and supporting the immune system.

What to Expect As the Ice Melts
When the ice begins to melt, look for the fish to become more and more active. When the water temperatures edge into the low 50's, consider resuming a feeding regimen with a wheat germ-based, easily-digestible food with low protein residues. Reducing protein in very cold water feeding regimens is good for the fish, and for the biological (bacterial) processes that reduces fish wastes and uneaten food. These processes work inefficiently in very cold water, so nitrogen may accumulate in cold pond systems when overfed a high protein diet.

Applying salt fights a variety of parasitisms, which may have gained an advantage against the fish in winter. Three pounds of salt per 100 U.S. gallons of water is recommended if you think there could be parasites in the pond. Remember, salt may harm plants – especially the ones that you're attached to.

Medicated food is highly recommended along with salt in the spring. It contains safe but effective levels of antimicrobials to help fight infection in the fish during the springtime warm up, and when their immune system has not regained its full strength.

Because hidden parasite problems and bacterial infections are the two most common diseases that people encounter with their pet fish in spring, I highly recommend salt and medicated food. Other medications can be selected, but salt and medicated food is easy to use.

For instructions on the use of salt, please see: www.koicrisis.com/medications/salt.html

For information on medicated food, please use: www.koicrisis.com/bacterial/medicatedfood.html

Preparation for Springtime
A successful springtime is not an accident. If your fish had a tough winter and your pond is not cleaned out in time for spring, poor health could be the result. In preparation for spring, you should recognize poor water conditions and poor fish health. Early detection could be the key.

Water tests for nitrogen may be useful to you. Making sure the pond is as clean as possible, but not "scrubbed" will help bring the fish into springtime in the best possible health. I do not recommend draining a pond and scrubbing the liner clean. Rocks, gravel, and an emerald green carpet of algae in the pond is a good thing and all contribute to the reduction of nitrogen and other fish wastes in the pond.

Spring Pond Cleanouts
In ponds that have balanced ecosystems with fish, plants, and plenty of space, the biological processes take care of problems which otherwise would require the use of gadgets and gear. However, there is a "climax" for all natural ecosystems. All riverbeds and ponds eventually turn into swamps as organic solids accumulate, filling them in over the years. On a very microcosmic level, this happens in your pond, too.

Cleaning your pond every year or so is good because it keeps the pond in the "new phase" with the best possible water quality where plants and fish can grow rapidly. My pond gets a minor cleanout of leaves in the fall after the last tree releases its leaves, and then a major cleanout in the spring.

How and When?
The best time to do this spring-cleaning is in the cool early months of spring, which varies from latitude to latitude. For Georgia, this would be late March and early April. In Chicago, April and May are usually a good time. Generally, when water temperatures are in the very low 50s, it is safe to hold fish in small holding tanks for a day or two with little trouble.

If you perform the cleanout in the cold water of late winter, where water temperatures are in the low 40s, it is too stressful to the fish because they are "just surviving" in the cold. On the contrary, if you wait until early summer when water temperatures are in the high 60s or low 70s, you've put yourself squarely in front of oxygen and nitrogen issues in small holding facilities.

I do not recommend removing all fish and doing a cleanout when the pond is warm, over 70° F. It can be done, and it can even be done very successfully, but it does require that those who are handling fish be well experienced and prepared to handle issues with oxygen depletion and nitrogen accumulation.

The Right Equipment and Methods
The tank used for holding your fish during the cleanout should be smooth-sided, round if possible, and covered with a net. It should be filled with pond water rather than tap water, and there should be an aggressive aerator, regardless of tank temperature.

The equipment should be sterilized before it's used on your fish to avoid the transfer of a virus or bacteria to your fish. Sterilization of fish handling gear is simply achieved with a misting bottle of chlorine bleach at a 1:30 dilution, then a clear water rinse and air/sun drying.

The fish should be netted in order starting with your favorite to your least favorite. This minimizes the "net chase" time for your best and favorite fish. It's even better if you can corral the fish to one end of the pond, minimizing the distance and duration of the chase.

No fish should ever be transported or carried from the pond to the holding tank in the net. This can cause their fins to shred and removal of scales and their protective skin slime. This is imperative. Instead, your fish should be apprehended in a net, then guided through the water to a small, water-filled bucket or tub for carriage to the holding tank. This method is especially important with fish of sentimental or dollar value.

What and When to Feed Them
The first food in the springtime should be easily digestible. Wheat germ based foods and Cheerios are popular, and for good reason. The fish like them and they are good "first foods" for spring.

Food should first be offered when the water temperatures achieve 50-53° F. Feeding should be sparing! If you load up the fish, they will load up the pond with fish wastes and the beneficial bacteria responsible for reducing the wastes will not be functioning optimally in cooler water.

I like to start with Cheerios until the water is 55° F and then I switch to any combination of two good quality foods. I highly favor pelleted foods for their convenience.

Your Role
For many water gardening enthusiasts, fish play a very important role in the pondering experience. Becoming knowledgeable about their care and how to help them make the best of a tough, wintry situation is well worth your time and effort. As the water warms, your fish will soon be welcoming you each day when you visit your pond.