The Secret to Small-lot Homesteading? Aquaponics!
By Jeremiah Robinson
You could say that I’m an odd duck. A homesteader and agriculturally-minded Mennonite, I grow a good portion of the food needs for my family — at least by dollar value — on my own land. This includes vegetables, greens, eggs, meat, and maple syrup. As the perennials get established, I’ll have my own fruit, berries, nuts, and plants grown for soil fertility.
The odd part? I live four miles from the capitol building in downtown Madison, Wisconsin, on an acre lot. Where I live, I face three major challenges in growing food:
• Limited space: One-quarter acre isn’t much to grow on, especially when much of it is shaded.
• Zoning regulations: City regulations make it tough for me to raise animals, especially for meat.
• Cold weather: In USDA Zone 5a, I see temperatures of -25 degrees F and only get 110 reliable frost-free days.
However, over the years I found a method for growing that allows me to overcome all these obstacles. Can you guess what it is? I’ll give you a hint: It was invented separately in ancient times by some creative folks in both China and the Amazon.
In China, it allowed subsistence farmers to thrive on plots of mountainside land that no traditional farmer could ever survive on.
It gave the indigenous residents of ancient Bolivia the power to develop a wealthy and sophisticated agricultural civilization atop worthless soil for 1000 years.
For the past two millenia, these farmers quietly developed the most efficient and sustainable method of growing food known to man. And nobody noticed.
However, about 50 years ago, some folks in Massachusetts calling themselves “The New Alchemists” rediscovered those old techniques and started adapting them to our modern world.
This ancient-turned-modern method of growing is called aquaponics. It combines the raising of fish (aquaculture) with the growing of plants in nutrient-rich water (hydroponics). The fish fertilize the plants, and the plants clean the water.
It’s a fantastic and labor-minimizing way to grow! It allows me to raise my own meat (fish) and grow the highest quality greens, all without weeding, mulching, fertilizing, or building soil. But those weren’t the challenges I needed to overcome. Let me come back to those.
I built my aquaponics system in a 8’ x 16’ greenhouse. This includes enough space for 480 gallons of water and 70 ft. of growing surface, as well as a seed starting area. This small space allows me to grow the following quantities of food each year:
• 50 lbs. of trout fillets
• 100 lbs. of cold-finished, foodpurged tilapia fillets
• 75 lbs. of basil leaves for pesto
• 50 lbs. of winter spinach
• 40 lbs. of lettuce
This adds up to a total farmers market value of $3,660, all from a small unheated greenhouse. Oh, and by the way, I don’t have to wash my lettuce and herbs since there’s no dirt and (usually) few pests.
In the city, I’m not allowed to raise walking animals for meat. This includes sheep, goats, meat chickens, rabbits, guinea pigs, cows, etc. But I discovered one animal they never bothered to write regulations about. Probably because they don’t bark, bleat, moo, escape, smell, eat wood siding, or mate in public, no municipality that I know of has any rules about raising fish in fish tanks. Some homeowners associations require that tanks look nice or match the décor, but that’s not hard. This year, the Wisconsin DNR decided people like me don’t even need permits to purchase fish from a hatchery. Problem solved.
Do you know what noise the snow makes when it gets really cold, and you walk on it? It squeaks. If you live in a place where the snow squeaks, you know what it means to worry about cold weather. Like squirrels, we store up plenty of tomatoes, potatoes, carrots, pesto, and applesauce for the winter. But we still crave our fresh greens when the world outside is white. Besides that, greens raised in the cold taste loads better than those raised in warm weather — if you can keep them alive.
Fortunately, I happen to maintain a day job as an energy efficiency engineer with a specialty in cold climate heating. I experimented with a lot of methods for insulating and heating my aquaponics system, but I eventually came to a conclusion that surprised even me.
We can raise fresh greens outside in winter using aquaponics, and it doesn’t even take much energy. It does take a bit of doing to set it all up for the cold, but if you include multiple layers of thermal protection, it’s entirely possible to raise your own greens and fish outdoors all winter long with only a small input of heat and electricity. The trick is to insulate and air seal everything — in order to prevent evaporation at night — as well as to keep your plants, fish, piping, and filters thermally separated from the cold outdoor air.
Conserving energy in this way allows your plants to maintain their health all winter and grow slowly. To speed up winter growth you add small amounts of supplemental fluorescent light for a few hours after dusk during the weeks when there’s less than 10 hours of daylight.
But Wait! Where Do I Start?
If this article got you excited and you want to start making progress, you can download a set of plans from one of the sources listed below. Look them up on Google, and you’ll find what you’re looking for.
• Zero to Hero Aquaponics System: Built from a chest freezer, treated wood, insulation, and pond liner, this system is maximized for cold weather (plan cost — $17 with freezer conversion plans).
• Barrel Ponics: Built from 55 gallon food-grade barrels. Designed for warm weather, especially missions to third world countries (plan cost — free).
• IBC of Aquaponics: Built from a food-grade intermediate bulk container (plan cost — free). Designed for warm weather.
Jeremiah Robinson owns Frosty Fish, a company devoted to bringing aquaponics to the North. Feel free to get in touch at www.frostyfish.com or 608-616-0463. Address: 944 Dane St., Madison, WI 53713.
The Fish That Grew Some Food in a California High School
By Susan Perreault
What do you get when you cross 1,000 worms with 12 fish, 80 high school students, and one yard of red lava rock? A garden that is virtually self-sustaining and grows food faster, taller, and lusher than in most conventional gardens.
Seniors at California State University, Sacramento, have introduced aquaponics to high school students at Luther Burbank High School in the south part of the city.
Cheyene Kenniston, Ryan Nowshiravan, Mary Xiang, and David Hill are all collaborating on this project on urban agriculture for their environmental science class. They didn’t want it to be some rote written thesis on a theoretical project, but a living working example of what urban agriculture could be for the average person.
“We wanted to make aquaponics more understandable for people to do themselves,” said Kenniston, one of the originators of the project.
A simple project, however, was not what the greenhouse was destined to be. The aquaponic greenhouse quickly took on a life of its own. The greenhouse is the cornerstone of one of the school’s most popular after-school programs. In addition, the seniors have given students in the high school’s special education department something unique to learn from and enjoy.
The goal of the project was simple. “We want to teach everybody about it because it’s such a great system,” said Sac State senior Ryan Nowshiravan.
In its most basic sense, aquaponics combines hydroponics with aquaculture. In aquaculture, fish or other animals, including crawfish, prawns or snails, are raised in tanks. The water from these tanks is used to water and nourish plants or seeds in adjacent beds. Ammonia is a natural byproduct of fish waste. If allowed to build up in the tank it becomes toxic to the fish. Bacteria covert the ammonia to nitrites and nitrates, then plants use these by-products as nutrients. As the water circulates through the porous rock bed, the nitrates and nitrites are removed by the plants and the water is filtered back into the fish tanks clean and free from toxins. Therefore, the aquaponic system creates the perfect closed loop system for growing plants and for growing fish! Though not done at Luther Burbank High, some people also use their aquaponic systems to raise animals for food. As the fish or other animals grow to sufficient size they are replaced by younger animals and the larger are used for food.
Aquaculture has been used for centuries in conjunction with farming, and is still used today. Farmers in China have added fish to the water of their rice paddies for over 1,500 years to add natural fertilizer to the water. In 1000 A.D, the Aztecs also used fish to aid in growing crops. They grew corn and squash on islands. In the ditches around these islands they added fish and mollusks that they raised as food. As the waste accumulated it was gathered from the bottom of the moats and used as fertilizer. Think of the natural fertilizers we use today; the fish emulsion we pay for in the organic supplement aisle works on the same principle.
In the spirit of eco-friendliness — and cost savings — the Sac State seniors used as many items as they could find at the school for their project. The school had been a former FFA site, but, with staffing changes, that program was disbanded in 2008. Many items were still left, however, to give the project a healthy boost. An abandoned 25’ x 30’ greenhouse was the perfect place to house the aquaponic set-up, and former grow tables were disassembled and their wood reused to fashion two – 5’ x 5’ x 12” beds. Two dusty 130-gallon plastic tanks were cleaned and became the homes for the fish that became the heart of the aquaponic system. The few items they actually purchased included two water pumps, a yard of 3/8” lava rock, pond liner for the wooden beds, and, of course, fish.
“We started with 75 one-inch gold fish,” said Mary Xiang, Sac State student and Burbank High alumnus who suggested this school as the site for the project, “all but six of them died.”
Poor fish choice and early hiccups with the measurement of the pH and ammonia levels caused the massive fish kill. However, as luck would have it, they were able to pick up three one-pound carp for free at the state fair during the summer.
“It was readily apparent after we added the carp,” said Nowshiravan, “we saw a jump in plant growth.”
The nutrient-rich water floods the grow beds approximately every six hours. The carp, being many times larger than the one-ounce goldfish, immediately increased the nutrients flowing to the system. The amount of nutrients in the water is directly related to the size of the fish. The bigger the fish, the more waste they release. The more ammonia, the more nitrates and nitrites and the more plants the grow beds are able to support. Once set up and equalized, the only regular maintenance required is feeding the fish, monitoring the water’s pH level, and adding small amounts of water to the fish tanks to replace loss from evaporation.
The students planted a variety of plants during the first months of the projects. Herbs, such as basil, rosemary, lemongrass, and lavender did well as did kale, iceberg lettuce, tomatoes, and bird pepper seeds. All the plants showed more rapid growth with the addition of the larger fish. The leafy herbs and lettuce grew in half the time they had before. That is one of the benefits of any aquaponic system.
“In aquaponics, lettuce can grow in 27 days. It takes 48 days with traditional farming,” said senior David Hill. The idea of urban agriculture has taken a solid hold among these college students; each one hopes to get jobs in sustainability or environmental science when they graduate.
The aquaponic grow beds that started off as a college senior project have become so much more for the staff and students at the high school. When the project was first proposed by the students to the administrators at Luther Burbank High, it immediately caught the eye of teacher Aaron McClatchy.
“When someone comes to your school and offers a project for free, your answer, as a teacher, is immediately ‘yes’,“ said McClatchy. He admits he wasn’t sure at first how he would use the students’ gift, but it became readily apparent that his special education students could benefit almost immediately. McClatchy uses the space to prepare his autistic and developmentally delayed students for life after high school. The students perform the aquaponic and garden maintenance tasks to foster independent living skills, including cooking, shopping, and self-management.
“It’s a great tool to use because there’s so many different things we can do,” said McClatchy.
His students have practiced a wide variety of tasks, from basic chores such as washing the gritty lava rock to more advanced projects such as taking the bus to the local big-box hardware store where the students bought and paid for greenhouse supplies. All of these tasks help the students with independent living skills like counting, using money, and following direction. McClatchy also uses the greenhouse and the adjacent garden as a calming space for the students when they are having a bad day.
In addition to the greenhouse, other unused spaces at the school have been brought back to life. Bare ground behind the school is once again irrigated and planted for seasonal vegetables. Abandoned cinder-block bins hold compost piles over six feet high. And an old cement block enclosure — once home to a diesel tank that fed farm machinery — now holds the worms that feed the fish. All of the students are expected to add to and maintain the compost and worm piles with scraps from the cafeteria and to “harvest” the fish food — worms, solider flies, and larva — by hand.
Over 80 mainstream and special education students at Luther Burbank High School use the aquaponic greenhouse and its adjacent traditional garden; almost 30 of those students do so voluntarily in the after-school program. A day spent watching these kids dig, weed, repair irrigation, and chop worm food is testament to the lure of urban agriculture.
“I just wanted to learn about gardening. It’s a good life skill and it can help you,” says senior Rovonia Delarosa Rowe. Her autistic schoolmate put his sentiment about the greenhouse even more succinctly. “It’s joyable.”
Why yes, Jose, that it is.
By Jeremiah Robinson
In my previous article, I introduced you to my little homestead in the city, and claimed that it was possible to grow year-round in a small space — in a cold climate — using aquaponics (fish and plants together). In this issue we get into the technical and theoretical details about the forces of creation that make it possible. And we make a new friend.
Today we get to learn about the most fun subject in all of thermodynamics. Can you guess what it is?
You’re right. It’s enthalpy!
When we talk about enthalpy, we mean the total thermal (heat-related) energy contained by a substance. In aquaponics, we’re talking about the heat contained by your water, your grow beds, the air in your greenhouse, and so on. It relates to temperature, but there’s more to it than that. And it’s a big deal. It’s crucial to understand enthalpy if you want to save energy in your cold climate aquaponics system. To illustrate why I think you and enthalpy should become friends, I’d like to give you a simple quiz.
1. How many BTUs does it take to raise 10 pounds of water from 40 to 50°F (4 to 10°C)?
2. How many BTUs does it take to raise 10 pounds of water from 30 to 40°F (-1 to 4°C)?
(Hint: The answer to these questions is not the same. See end of article for the big reveal.)
The reason that the answer to question two so greatly exceeds question one is that to get from 30°F to 40°F water, you can’t just raise the temperature. You have to change the state from solid to liquid by providing the ice with the heat of fusion. While raising one pound of water 1°F takes one BTU, changing one pound of ice to liquid water takes 144 BTUs. In other words, it takes the same amount of energy to heat water from 31 to 32°F (-0.5 to 0°C) as it does to heat from 32 to 176°F (0 to 80°C).
When you apply heat to a material to raise its temperature, we call that sensible heat. When you apply heat to change its state, we call that latent heat. The total (thermal) enthalpy of a material includes both its latent and sensible heat, or: Enthalpy = Latent Heat + Sensible Heat.
What’s a BTU?
In the United States, we measure heat in British Thermal Units, or BTU. One BTU is defined as the amount of energy it takes to raise one pound of water 1 degree
In Metric, 1 BTU = 1060 Joules and
1 pound = 0.45 Kg.
So far we’ve talked about solid and liquid water, and that’s fairly simple (oh sure, easy for me to say). Well, hold on to your hats. Things get complicated when you start talking about water vapor.
You might have thought that we don’t have to worry about enthalpy with regard to the liquid-to-vapor transition because we won’t be boiling our fish. But you’d be wrong.
Molecules vibrate. Molecules near the surface of a liquid can sometimes vibrate enough to launch themselves off the liquid into the air. This is called evaporation. Molecules crashing into any material and sticking to it is called condensation.
If people evaporated, it would mean that every time anyone got really angry they would shoot off into space. When they cooled off they would fall back down and “condense” into the earth. Might have interesting implications for our culture. But I digress.
The conditions that cause molecules to launch include the temperature of the water and the temperature and relative humidity (RH) of the air. Some examples:
• At 100 percent RH (relative humidity), the same amount of water evaporates from a surface as condenses on it.
• At 10 percent RH and 100°F air temperature, when you sweat you don’t feel it because the water evaporates from your body so quickly. You do get kind of salty, though.
• A tray of water at 80°F (27°C), surrounded by air 80°F and 50 percent RH, about one pound (0.45 Kg) of water will evaporate per square foot (0.09 m2) of surface area per day.
The thing about this whole launching and condensing process is that it involves a lot of energy. Each launching molecule absorbs a ton (0.91 metric tons) of heat on its way up, and releases it all on its way down when it condenses. Half of this heat comes from the air, and half from the surface (i.e. the water or your greenhouse plastic). This heat, called the heat of evaporation, equals a whopping 970 BTU/lb.
Applying Enthalpy in Aquaponics
First of all, you should look carefully at every place in your system where water is exposed to air. Any exposed liquid surface area offers a place where water can evaporate, taking its 970 BTU per pound along with it. This is also the reason why I sometimes have to heat my fish tanks to keep them at 80°F (27°C) when the outdoor air is 90°F (32°C) and dry.
Evaporation makes trouble for all of us in aquaponics, but here’s how you can tell if it’s a major problem for you. Each morning in winter, check to see how much ice has frozen on to the inside of your greenhouse plastic. If the outdoor temperature is below zero and you have some ice, don’t worry about it. However, if you still get ice when the outdoor temperature is 15, then you have an enthalpy problem.
To resolve your evaporation enthalpy problem, you need to do two things:
1. Reduce the surface area of water in contact with air. This includes your fish tanks, grow beds, and the surface of your plant leaves. It also includes the inside of your flood and drain beds, because when you drain them, they fill with air that can’t wait to evaporate all the water left on the huge surface area of your media. Dry air is trouble.
2. Insulate and air seal the exterior of your greenhouse. Use double or triple wall glazing. Insulate the north, east, and west sides. If you can, insulate the top of your greenhouse on the north side. All of this serves to raise the temperature of the greenhouse surfaces above the dewpoint, or the surface temperature at which vapor will condense. Every drop of condensation that forms in your greenhouse is another drop that has to come out of your aquaponics system.
Now that you’ve resolved all your evaporation issues, you should turn to the remaining 144 BTU/lb (334 kj/kg) that results from melting and freezing. This side of enthalpy will likely work in your favor. Not only does it make it difficult for the water in your system to freeze, but it also gives you a great way to store energy. It stores this energy in something called thermal mass.
Thermal mass signifies an object’s ability to store heat. Metal, for example, stores heat very poorly. You can heat a pan until it’s red hot, then let it cool for 20 minutes and touch it with your hands. But I wouldn’t do the same thing with a concrete pan — it’ll burn you! True, the only reason you’d ever find a concrete pan is because you wanted to do a thermal mass experiment, but still …
Thermal mass basically correlates with weight. Heavy things store more heat. But there is one exception to this rule, and it relates to enthalpy.
Liquids near their freezing point contain an incredibly large amount of thermal mass. A 55-gallon drum of water contains 458 pounds of water. To reduce that drum’s water from 32 to 31 degrees would release 65,894 BTUs. That’s more than some furnaces, and we’re talking about one drum.
Cold water is thermal mass on steroids. If thermal mass were NASCAR, cold water would be Richard Petty.
Even better, the temperature we’re trying to maintain in greenhouses for cold-weather crops is often at or near 32 (0°C). Having a huge quantity of thermal mass that really, really doesn’t want to drop below 32 degrees will help with that. A lot.
1. 100 BTU; 2. 1540 BTU
Using Aquaponics to Dress Up the Winter Garden
The Fish Factory
By Jeremiah Robinson
In the past two articles, I’ve started to give you ideas about how to grow outdoors in cold weather using fish and plants (aquaponics). First, I told you about what I’ve been up to, and then I confused everyone by talking about thermodynamics and enthalpy. This edition, we move on to something a bit more down to earth.
You may find it surprising to learn that the inspiration for my aquaponics design strategy came from heavy industry. As an engineer working with energy efficiency in factories, I noticed something striking: Factories are not like houses.
In houses, we heat air. Because we move from one room to another and want to stay comfortable everywhere we go, we keep our whole house warm. This generally requires heating the air in the house above a certain setpoint — say, 68°F (20°C).
On the other hand, factories only heat the things that need heating, and they keep those things as separated from the rest of the factory as possible. For example, I visited a paper factory in Wisconsin with a process that requires heating a chemical solution to 4,000°F. A few feet away, another process requires cooling another material down to 50°F. Keeping these processes thermally separated required some serious engineering. Most people who grow using aquaponics outdoors in the cold (usually in a greenhouse) treat their system like a house—they heat the air. But when you really get down to it, aquaponics is more like a factory than a house.
Here we see all the different factory processes involved in aquaponics. I call them thermal zones. I’ll tell you about each of them and their requirements, and then we’ll learn how to separate them thermally.
Fish Zone: The fish live here, in the water. The requirements depend on the type of fish. With the fastest-growing kind of fish — red Nile tilapia — this zone should stay above 80°F (27°C) for maximum growth. For other kinds of fish, temperatures vary greatly. Arctic Char, for example, find their happy place around 40°F.
Transport Zone: This zone moves our fish waste between the other zones. The transport zone includes any solids filtration devices, such as swirl or suspended solids filters. The only requirement for this zone is that the water shouldn’t freeze.
Nitrification Zone: This zone converts fish waste into the epic nutrients that create the massive growth that made aquaponics famous. The organisms that live in this zone vary in their effectiveness based on temperature, providing the maximum nutrient conversion rate at 85°F (29°C), continuing to nitrify at reduced rates until they hit 32°F (0°C), when they stop. Below 32, the organisms don’t die but do sort of get stuck in one place (in the ice). The main thermal requirement of the nitrification zone is that temperatures don’t change too quickly because the warm water organisms go to sleep faster than the cold water ones wake up (and vice-versa).
Root Zone: The thermal requirements of this zone depend on the types of plants you grow. Tomatoes, for example, grow slowly with root temperatures below 70°F (21°C), while spinach does just fine down to 40°F (4°C). On the other hand, many root diseases — such as pythium — wreak the most havoc at warm temperatures. Temperature swings also matter to roots, and some plants cannot tolerate dramatic changes.
Leaf Zone: This varies even more dramatically than the root zone does. Some plants require that temperatures never drop below 50°F (7°C) while others tolerate temperatures as low as 5°F (-15°C) without serious damage. Humidity also matters a great deal.
Everything Else: This includes everything outside your aquaponics system. In a greenhouse, it includes the area above and around your plants. It includes the area you walk around in and where you store fish feed and tools. From a thermal perspective, the only time this area has any requirements at all is when you’re there, which generally only occurs during the day. Unless, of course, your aquaponics system includes a hot tub (which I highly recommend).
Put Up Barriers
In winter aquaponics, you need to put up barriers between zones. These barriers fall into two major categories: insulation and air sealing.
Adding insulation to each component protects it from heat loss through the walls of that component. In some cases, you can make the walls themselves out of insulation.
Air sealing takes a bit more explanation. You just need to know that any time water comes in contact with air (including through your leaves which evaporate water using transpiration), a lot of energy leaves your system.
The best way to insulate and air seal your fish zone is to build it out of an existing highly insulated and air-sealed container. The best container on Earth was invented in 1834 and has been improving ever since then, through 180 years of engineering. Many of us have one in our homes. Can you guess what it is?
That’s right — a freezer! A chest freezer, modified through the use of potable water-safe epoxy paint, makes an incredibly well-insulated fish tank. The lid and gaskets maintain an almost-perfect air seal, minimizing water-air contact.
Assuming you’re using PVC pipes rather than open channels, air sealing is largely under control. We insulate the pipes using large diameter commercial pipe insulation, which you can purchase at your local plumbing supply house.
Because many of these supply houses refuse to serve homeowners, you may have to come up with a business name (“your name & sons plumbing” tends to work well) and walk in with a serious expression and work boots. Bring along a section of pipe to make sure you get the right size.
Alternately, you can buy large diameter swim noodles from the end-of-season sale at your local big box store.
You insulate filters (including nitrification filters or biofilters) by surrounding them in rigid insulation (flexible insulation becomes useless when wet). This includes board (pink or blue) insulation and spray foam. I use foil-faced board insulation, which I wrap around the filters (mine are round) by cutting through one side of the foil but not the other to make it fit around a curved surface, and then gluing it to the filter itself.
To make it pretty and weatherproof, you can surround the insulation with cut needed flexible plastic such as a piece of shower-surround.
The recommendations from this section also apply to any solids filters.
For this zone, the easiest way to insulate and air seal is to build the entire grow bed out of insulation with a structural frame, using a potable water-safe pond liner to prevent leaks.
Using another sheet of insulation for the top, with holes cut into it for insertion of net pots, allows for air sealing and insulation of that portion. I recommend allowing the insulation to rest on the edges rather than float on the water, as it creates a better air seal that way.
This zone creates the largest challenge for insulating and air sealing. Most growers don’t even try. However, when you set to work on it creatively it’s not that hard. The simplest method involves creating Eliot Coleman-style low tunnels over the grow beds.
Using a fabric-style low tunnel (as shown in the picture) provides insulation but no air sealing. It also blocks a significant portion of the sunlight. A plastic low tunnel would provide some of both insulation and air sealing, while letting more light through. You can air seal by fastening it to the grow beds or creating a removable low tunnel with its own structure, but it’s essential to allow yourself a way to open it up during the day and on warm nights so that plants can transpire when temperatures rise above 40°F (4°C).
The only reasons to insulate or air seal the rest of your greenhouse are as follows: A desire for comfort when you’re in there planting, harvesting, hanging out, or feeding your fish.
It provides a space in which to add thermal storage.
This last point flies in the face of most existing aquaponics design strategies, which focus nearly all their attention on air sealing and insulating the “Everything Else” zone which — in my humble opinion — is a waste.
The Best Fish for a Cold Climate
By Jeremiah Robinson
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 one third 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 or no 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 a 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 slowergrowing 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.
Choosing Plants for Winter Aquaponics
Over the past eight months we’ve been learning how to do aquaponics in greenhouses in cold climates. For the last installment in this series, we look at plants and fish that thrive in the cold, and how to raise them.
By Jeremiah Robinson
I grow in a cold house. In greenhouse language, this means I allow my temperatures to drop below 10˚F — cold enough to kill most plants. Others grow in warm (>32˚F) or hot (>50˚F) houses, which are nice and plush but in my climate require you to sell your soul to the electrical utility or burn up your woodlot.
I grow in cold house conditions because I want my aquaponics to produce more (in vegetables and fish) than I put into it (in energy). My super well-insulated aquaponics system does just that.
As you can tell, I’m proud of my energy efficient frozen tundra system.
While my cold house puts limits on my choices for plants, the ones I like the best are the ones that love the cold.
I’ve had success with the following list of plants in cold temperatures:
• Spinach (Giant Winter, Tyee)
• Swiss Chard
• Arugula (Sylvetta)
• Lettuce (Winter varieties survive down to 20˚F)
• Corn Salad, a.k.a. Mache and Lamb’s Lettuce
Perhaps the Popeye watching as a kid did it to me, but I love spinach more than any other food on Earth. This is lucky because of all the plants I mentioned, spinach grows the best in the cold. With its strong susceptibility to Pythium, it’s a challenging crop to grow. However, I’ve fought this battle and come out victorious. The following instructions work for spinach, and will suit the other (easier) plants just fine.
In growing spinach, you must know your enemy.
Coming in many varieties, the Pythium fungus will kill every single one of your winter spinach plants before you can finish your sauna and ice dip.
With Pythium, prevention is the only solution. Where tomatoes and lettuce will tolerate less than ideal seed-starting conditions, for spinach you must follow these recommendations (or their equivalent) exactly:
1. Use either brand new sterile media, or sterilize it yourself by boiling 30 minutes or pressure cooking to 15 pounds.
2. Soak your trays and cells in five percent bleach solution for 20 minutes minimum, then rinse three times.
3. Dip your seeds in the bleach solution, then rinse.
4. Start your seeds in the seed tray with humidity dome — maintained between 50-70˚F — by planting them at ¼-inch depth. (Alternately, you can start your seeds in paper towel with water/peroxide mix, and transplant sprouted seeds.)
5. Each time you water, mix 10 parts water with one part hydrogen peroxide solution. Provide no more than 13 hours of light. Providing only eight hours will make your plants bolt-resistant once they’ve grown to full size, though they start slower this way.
6. Once they’re 4-inches tall, harden off your plants for several days, at times when greenhouse temperatures will not drop below 32˚F.
7. Transfer plants to the aquaponics.
8. Once planted, the intense biological community in aquaponics (especially with water temperatures at or below 50˚F) helps protect you from pythium.
With the hard work done, all we do now is maintain proper humidity and light. Plants need to transpire to grow, and most do so most effectively between 50 and 70 percent Relative Humidity (%RH). Under high humidity conditions (common in winter greenhouses), water can also condense and drip on your plants encouraging disease.
During the day, I manage humidity in the low tunnels over my grow beds by bringing in cold, dry air from the outside and pre-heating it using a low wattage hair dryer, controlled by a 120-volt dehumidistat. A heat recovery ventilator (HRV) would do better, but they’re expensive.
At night we get a free pass from humidity. In fact, the more the better!
As temperatures fall below 40˚F at night (i.e. in low light conditions) humidity becomes a resource rather than a problem. Because the plants stop transpiring at these temperatures, growth is not a factor and diseases are rare and largely dormant. Water condensing on plant roots and greenhouse (or low tunnel) walls releases heat that keeps your plants warmer than the air.
With regard to light, the choice is up to you.
My latitude doesn’t provide enough light for significant plant growth. Because of this, I supplement in small amounts using fluorescent lights attached to the undersides of my low tunnels. With lettuce, you can leave the lights on all night long if you want, which allows for fewer lights. For spinach, however, 13 hours is the maximum to prevent bolting.
Depending on the temperatures you maintain based on your climate, and the amount of light you supplement, you get anywhere from zero to 100 percent growth rates. If you choose not to supplement light, you should grow your plants to full size prior to November 1. While they won’t grow much over winter, you can still harvest all winter. Carbon dioxide (CO2) helps with growth at low light conditions, and the CO2 released from fish waste decomposition helps with this.
Harvesting greens that have frozen and thawed improves the taste! However, it’s a bad idea to harvest while your plants are still frozen.
It’s also a bad idea to let your lettuce freeze too hard (below 25˚F) or too often, or they’ll die.
Avoid harvesting more than 30 percent of any plant that you want to keep growing. This is an important practice, because in late winter as temperatures warm, your plants (which spent the winter building an impressive root structure) will take off like rockets.