The Best Fish for A Cold Climate
A Series on Aquaponics, Part 4
By Jeremiah Robinson, Wisconsin
If you read my other articles, you’ll know that I live in one of the colder parts of the country, in Wisconsin. During the polar vortex two years ago, every one of the Great Lakes froze solid and I wrestled with this question of what to do with my fish in winter.
Sitting in the warm greenhouse while the wind whistled by outside, I had a long talk with my fish and they gave me four options for what to do with them when it gets cold.
1. Shut the system down.
2. Harvest your warm water fish and switch to cold water fish.
3. Raise fish that can survive both warm and cold water, year-round.
4. Breed fish yourself, indoors in the winter.
Each choice offers benefits and drawbacks. We’ll discuss them each here briefly.
In the March 2014 issue of Aquaponics Survival Communities, Travis Hughey (of barrelponics fame) wrote the following:
“Many people keep their aquaponics systems up and running through the winter months. We used to do the same, but the past two seasons decided not to. The primary reason is economic. The expense of keeping things going and heated is just too high for what produce we do get since we preserve the bounty from the previous growing season.”
Shutting down the system offers probably the simplest option. If you shut down for winter, you don’t need to insulate or air seal your system as thoroughly. You don’t need to shovel the path out to the greenhouse after every snowfall. You cut your second-biggest expense (heat) by at least 50 percent.
The negative consequences for winter shutdown include missing out on succulent winter spinach, several months of lost fish growth, an inability to raise fish, which take multiple seasons to grow out, and the requirement that you re-introduce the nitrogen cycle in the spring.
I should note that, if you live where it drops below 70°F at night and you don’t have a well-insulated or air-sealed system, you will still have to heat your water—regardless of what fish you raise—because evaporation robs a great deal of heat even in the warmer months.
HARVEST AND SWITCH
Last winter, I chose this option for my aquaponics system. In early October when nighttime temperatures first hit freezing, I harvested all my tilapia for the freezer and drove to my local hatchery for some rainbow trout. In early June I harvested the trout before the heat of summer set in.
The advantages to switching fish include maximizing the fish harvest from your system, getting a different flavor of fish in your diet, and maintaining a high level of nitrates in your water for vigorous winter plant growth (if you can maintain leaf zone temperatures as shown on next page).
Disadvantages to the fish switch include increased costs of larger stocking fish (you must buy bigger fish in order to grow them out in six months), regular water changes if your plants don’t take up enough nitrates (I change onethird of the water each month), the need to run lights a few hours a day if you want strong growth in December and January when the days run short, and the requirement to heat the water to near 80˚F to grow out tilapia in one season.
One false disadvantage that many warned me about is that “trout are finicky.” While they do require high dissolved oxygen levels, reducing the temperature of the water allows oxygen to dissolve more readily and aerators don’t cost that much to buy or operate. Supposedly trout also require a higher level of water quality, but I did not find this to be true. With nitrate levels surpassing 500 and lots of solids floating in the water, I lost a grand total of zero trout due to water quality. (I did lose some from a chelated iron overdose. Ask me about that another time.)
Another issue I had worried about was nitrogen conversion rates. At 50˚F, according to the books, nitrifying bacteria begin to go dormant. Again, not for me. I checked in with the bacteria regularly through the winter and—to my relief—never found a measurable amount of ammonia. I use flood and drain media beds, so I can’t speak for deep-water culture, which might require more filtration or the addition of some kind of media to provide the bacteria surface area to live on.
Some fish types survive in both cold and warm water. These include perch, catfish and largemouth bass.
In addition to raising trout last winter, I also raised catfish in a separate tank. This worked well because with my 50˚F water temperature, they added little to the nutrient load but will grow quickly come warm weather. Within this option, you get three additional choices:
1. Allow your fish to lose weight in winter with 35˚F water (as they would in the wild). One possible complication of using 35˚F water is a risk of frozen pipes when you run your pumps for filtration, though you wouldn’t have to run pumps much if you feed your fish every two weeks like the DNR recommends.
2. Heat the tanks to the moderate temperature of 50˚F and experience minimal growth but no weight loss.
3. Heat to 65˚F, which allows your fish to gain a reasonable amount of weight over winter.
Advantages to year-round fish include the option to purchase fry or fingerlings for less cost than larger fish, the ability to grow more fish types including perch(considered by many the best tasting freshwater fish), a reduced nutrient load requiring fewer orno water changes in winter, and the option to raise them together with other summer- and winter-specific fish if you have multiple tanks or compatible breeds.
Imagine cozy and romantic nights by the fire…with your fish.
If this appeals to you, you might like to bring them indoors in winter.
Doing so (with a good air-sealed system design) allows you to forego much of your winter heating bill. You can raise warm weather fish in winter, and grow them out year-round at fast growth rates.
Disadvantages include the requirement that you build either two aquaponics systems or a portable one, the fact that aquaponics systems require minimum 100 gallons for stability which requires some space in your home, and the need for significant supplemental light to grow plants.
Moving indoors also allows you to breed your own fish. I cannot claim any experience with breeding, but I do know that it offers one major benefit. If you do it right, you don’t have to purchase fish at all except to widen your gene pool. For me, driving to hatcheries and purchasing fish makes up the largest yearly cost of running my aquaponics system. With breeding, the cost savings are substantial.
Disadvantages to breeding indoors include a limit to the types you can breed yourself, the requirement for indoor breeding tanks, the noise of an aerator when you want to sleep, and the potential for mold in an over-humidified room. If you breed tilapia, this requires you to either purchase or produce a super-male (yes, that’s a real thing) or make do with slower growing mixed-gender stock.
As possibly the simplest breeding solution, raising mixed-gender tilapia together with largemouth bass allows the tilapia to breed prolifically (as they do) and the bass to eat all their fry. When you want more tilapia, you simply take a few fish into a separate tank and allow them to breed for a time.
HOW TO DECIDE
This article assumes that you already own an energy-efficient, air-sealed, insulated aquaponics system. The outlook is a lot different without that.
Despite its significant benefits, designing and building an aquaponics system for use in the winter in the cold parts of the world—depending on how you do it—can mean biting off a bigger piece of work and worry than building and operating a system for warm-season use alone. Adding in a breeding tank adds another item to your mental list of things to keep track of, while it too adds value.
Still, if you ask me, given the sunk cost of a greenhouse, fish tanks, pumps, aerators, grow beds, and fish, from an economic perspective it makes the most sense to spend a few hundred dollars and a few hours more to build an energy efficient cold weather aquaponics system to max out the production capacity of that initial investment. You can do this by rotating your fish seasonally, growing fish that survive year-round, or both.
But just like everything, it’s your choice. At the end of the day, you decide where you want to put your efforts in homesteading. Swimming against the flow of mainstream culture takes energy, and none of has an unlimited supply. Whatever you choose to do with your fish and your homestead in your community, the rest of us will be here to support you.
We’ll also be here to pick up the conversation again next month.
This is Jeremiah Robinson’s fourth piece in Countryside. Look for more from him in upcoming issues.