Aquaponics combines fish and plants in a closed, circulating system. It is a great way to produce food rapidly and in a small space. Yet, if you live in a cold climate, you may soon find that you face challenges that make you envious of your southern colleagues. That said, with good planning you can develop a system that will thrive for years to come.
Start With Seasonality
Generally speaking, aquaponics is considered a year-round endeavor. Nevertheless, if seasonal growing will be a better fit for your lifestyle or business, you might consider two or three season aquaponics systems. The number of seasons you plan to use the system will influence how you design it.
Where to Keep Your System
There are three basic options for setting up your system:
- Outside unprotected
- Outside in a Greenhouse
Indoors you can easily maintain your system year round. The system could be as small as an aquarium by the window or as large as a basement system with artificial lighting. An outside system without any protection will be, at most, a two to three season system. That said, there are some techniques to extend the season. For instance, you could warm the water in your system, allowing it to tolerate lower air temperatures, though preferably with some sort of solar collector as opposed to an electric heater. You could also easily extend your season by covering the system with a quality frost blanket. I personally have had a raft-type system, which is warmed in part by its large volume of water, survive air temperatures as low as 25 degrees Fahrenheit (-4 °C) with a quality frost blanket.
If you decide to house your system in a greenhouse, consider whether or not you wish to heat the system. Conventional greenhouses with heating and cooling equipment can use significant amounts of electricity and natural gas or propane. Weigh this energy investment against how much produce you will be able to grow and how you plan to use it. If you choose not to heat your greenhouse, be aware that depending on how cold your region is, the greenhouse may not extend your season much, unless you take measures to trap and retain heat. Passive solar, home-attached, and Chinese style greenhouses are designs, particularly built by DIYers, that can notably reduce the need for energy inputs. Even so, a conventional greenhouse can be improved with ground insulation, thermal blankets, thermal mass, and other techniques.
How to Heat Your Greenhouse (if applicable)
There are numerous ways to heat a greenhouse during colder months. What makes the most sense for your greenhouse will depend on the size and type of the greenhouse, your budget, readily available resources such as wood, and your own technical expertise. Options include:
- Natural Gas
- Wood stoves
- Rocket mass stoves
- Ground source heat pumps
- Solar hot water collectors
- Solar air heaters
Generally speaking, heating the water or thermal mass in the greenhouse will be more efficient than heating the air. The types of fish and crops you choose will determine how much you will need to heat your greenhouse.
Choosing Your Fish
Although tilapia is a popular aquaponics fish and has its advantages, it is not ideal for cold climate aquaponics. Its ideal temperature for growth is roughly 80+ degrees Fahrenheit (27+ °C), meaning that you will need to use significant energy inputs to keep the water warm. Instead, consider a cool water species such as walleye, carp, koi, yellow perch, or bass. Not only will you not need to worry about your fish dying if the temperature drops, but you can establish a system that uses minimal energy. Keep in mind that if the water temperatures become very cold, your fish may eat notably less and the bacteria driving the aquaponics process will slow down.
If you plan to establish a two or three season system, the fact that your system will grind to a halt is very convenient. You may find it necessary to have a small electric heating element trigger if temperatures become extreme and threaten to freeze your water. Additionally, you can help your fish survive by insulating around your tank or having your tank set into the ground. Alternatively, you can always choose to bring your fish inside during the winter and host them in a basement or aquarium aquaponics system.
What Crops to Grow
Ultimately the crops you choose to grow will depend on a variety of factors. Whether you set up your system indoors or outdoors, in the summer you will be able to grow a wide variety of crops. In cooler months, however, it is best to choose cool weather tolerant crops. Consider experimenting with following:
- Pak Choi (Bok Choy)
- Swiss Chard
Ultimately your success in cool weather will depend on:
- Having a well-functioning system with the right balance of fish & fish feed
- Length of day
- Air temperature
- Water temperature
- A little patience
If you have a system where the water temperature drops to the point where the fish eat less, the rate of growth of your vegetables may slow dramatically and you may need to wait patiently for your next harvest. Keep in mind that the shortest day of the year occurs on the winter solstice in late December. At certain latitudes you may find that you are unable to grow crops at all in the winter without supplemental lighting. Note also that some plants, such as some onions, are “short day” plants which may flower as the nights become longer.
Experience Is the Final Word
After you have designed and built your system, be prepared to experiment. Experience will teach you what crops work best, what pests you may encounter, and how well your system handles the cold. You undoubtedly will need to make changes through time. Just remember that cold climate aquaponics is more energy intensive and the more ways you can find to reduce your need for electricity and heat by choosing carefully your fish, plants, and aquaponics system, the more successful you will be.