10 Do’s and Don’ts of an Aquaponics Greenhouse
By: Kari-Lise Boyer
There’s a multitude of resources on aquaponic growing, and on building a greenhouse. But what about using aquaponics in a greenhouse? What are the best practices, and things you need to watch out for? We’ve rounded up our top 10 recommendations for designing a year-round aquaponics greenhouse.
- Do Sketch out your Floor Plan
It cannot be overstated: creating a floor plan at the beginning is imperative. Space-
efficiency is key in an aquaponics greenhouse, where fish tanks and equipment occupy floor space. Ensure all floor space is used efficiently, since this is space you pay to build and operate. Round fish tanks fit awkwardly in a rectangular greenhouse, leaving un-used space in the corners. Rectangular tanks may be a better choice for small greenhouses, though there is some debate about which is better for the fish.
If unsure where to start with your plan, we recommend first determining the size of growing beds. From there you can determine the necessary fish tank volume (see a book like Aquaponic Gardening for basic rules of thumb). Once you know the size of each of these elements, you can then lay them out on paper, and work backwards into the size and shape of a greenhouse. Use examples as inspiration, like the floor plans available at Ceres Greenhouse aquaponics page.
2. Don’t Place Fish Tanks in Direct Sunlight
Direct sun on fish tanks fosters algae growth and can overheat tanks. As a general rule, it is much easier to heat tanks than to cool them. There is a multitude of ways to heat water, but cooling it with chillers is very expensive. (Ideally, you don’t have to do much of either with an efficient greenhouse.)
To keep tanks out of direct light, you can shade them using a section of roof insulation. At Ceres Greenhouses, we locate fish tanks along an insulated North wall of the greenhouse; a partially insulated roof blocks intense summer light. They get some heat gain in the winter. This also helps keep tanks in the most stable temperature zone (furthest away from the glass or plastic glazing materials). Since fish have a narrower temperature range compared to plants this is best for both worlds. In large commercial aquaponics operations, we recommend using a separate insulated room for fish tanks.
3. Do Know Your Temperature Requirements
Three different biological systems occupy your aquaponics greenhouse and all have certain temperature requirements. Fish and plants temperature ranges varies based on the varieties you select (e.g. cold water v. warm water). The third element is the bio-filter, the bacteria and worms that convert fish waste to fertilizer. Bacteria thrive in warmer temperatures, between 70 and 90 F.
An important part of the greenhouse planning process is to identify these ranges, and then think about how your structure will maintain them. Unlike homes, easily controlled with a thermostat, greenhouses require more forethought. Before you invest in a structure, talk to greenhouse companies about your minimum temperatures and what heating / cooling equipment is needed. Ask them to forecast energy costs, or do this yourself using an online heat loss calculator.
Methods for heating / cooling a greenhouse vary widely depending on your operation and climate. Propane or electric are most common, but energy-efficient and renewable systems are possible too. At Ceres we use a system that stores solar thermal energy in the soil underground. Called a GAHT system. It provides year-round heating and cooling for the greenhouse. Solar hot water systems provide both water and space heating for larger commercial greenhouses. The 2,400 sq. ft. aquaponics greenhouse at The Sage School in Sun Valley Idaho, for instance, is heated entirely with solar hot water. (You can learn more on integrating solar hot water in our recent book, The Year-Round Solar Greenhouse).
4. Don’t Skimp on a Greenhouse
It’s likely that you’ve invested, or are about to invest, a good deal of time and money into your aquaponics system. It’s wise to protect this investment with a durable structure. Low-quality greenhouses are not engineered for wind or snow loads and will collapse under severe conditions. Plus, they are very inefficient energy-wise. Made with thin, low-quality materials, they require lots of heating and cooling to grow year-round in most climates.
For example, an aquaponic grower in Boulder, Colorado purchased a low-cost polycarbonate greenhouse kit from a hardware store. During a cold snap, his water heater broke, and the poorly insulated greenhouse quickly froze. Instead of a thriving aquaponics system, he had fish popsicles. The photo below shows a Colorado greenhouse kit that was torn down in high winds just a few months after it was built.
Ask greenhouse manufacturers, designers or builders about their warranties and the anticipated operating costs. Upgrading to a durable, energy-efficient greenhouse usually pays off within a couple years.
5. Do Insulate!
At Ceres Greenhouses we build greenhouses with highly insulated walls and a quality polycarbonate roofing material to enable greenhouses to grow year-round even through harsh winters. For our aquaponics clients, we also recommend insulating several other areas, namely anywhere water circulates. Water heating is usually the largest operating expense of a cold-climate aquaponics greenhouse. Insulating both fish tanks and plumbing can cut heating costs dramatically. For example, if your plumbing runs underground, simple pipe insulation prevents the cold soil from sapping heat from water. Malleable insulation like bubble wrap helps maintain fish tank temperatures.
6. Do Bury Tanks
Another way to reduce water-heating costs is taking advantage of the natural
insulating properties of the soil. Burying fish or sump tanks not only helps keep the water temperatures more stable but saves space as well. This strategy depends on your aquaponic system design. In a basic flood and drain, such as the one shown at Growing Power below, fish tanks can be buried underground. If using a system that requires sump tanks, like the Constant Height One Pump (or CHOP) system, the sump tanks are often buried partially underground and the fish tanks left above ground.
7. Don’t Leave Plumbing to the End
When setting up your system, installing plumbing is often left to the end, after the fish tanks and beds have been installed. Keep in mind, though, that plumbing may have to cross the greenhouse. If you don’t want this on the floor it should be installed before flooring, buried underground. Also consider that you may want to access plumbing in case to fix a component or expand your system. Thus, we find a good flooring choice is brick pavers or flagstone. They create a level surface that can still be altered if needed.
Concrete floors are also popular for aquaponic greenhouses. They create a smooth easy-to-clean floor, and make rolling equipment easy. Keep in mind, though, that with concrete plumbing typically lays on top of the floor and creates a slight tripping hazard. For more on greenhouse flooring options see Ceres blog on the topic.
8. Do Cover Tanks (when possible)
The biggest surprise for most first time greenhouse growers is humidity. Greenhouses are naturally humid environments because plants evaporate water as they grow. Fish tanks and sump tanks increase humidity as water evaporates from their surfaces. High relative humidity can be problematic: it hinders plant growth and increases the risk of molds, mildews and pathogens. Thus, controlling humidity is a major challenge for aquaponic growers. It can be controlled with a number of methods, proper ventilation being the main one. Another tactic is to cover tanks so that they don’t constantly waft water into the air. Loose plastic sheeting or a more robust cover can be used to keep water in the tank, not the air. If covering fish tanks, you may need to supplement with an aerator to properly aerate the water. A cover can also help insulate tanks and reduce heat loss from evaporation, as on the Frosty Fish aquaponics blog.
9. Don’t Use Exposed Wood
Humidity also affects the materials in a greenhouse. One to stay away from: soft woods, like pine, and some wood composites like oriented strand board (OSB). Both can easily rot and deteriorate, and have very short lifespans in a greenhouse environment. We recommend metal and plastic materials that hold up better under moisture and condensation. If you do use wood, it should be well painted. We discuss how to choose durable materials for year-round growing in-depth in our webinars and courses on designing solar greenhouses.
10. Do Plan for Expansion
“You can never have too many outlets,” advises one of our aquaponics clients. Plan for your system now, but also think about how it may change if you expand, both the additional space needed and the added electric load. Designing this in from the start is much easier than retrofitting later. When wiring the greenhouse, talk to an electrician about your current electric load, and possible additional equipment. You may also want to plan some tolerance in case your current system doesn’t perform as expected… What if you need an extra water heater or aerator? As Donald Rumsfeld said, there are known unknowns and then there are unknown unknowns… We suggest planning some extra capacity. More on planning electric requirements in The Year-Round Solar Greenhouse.
Ceres Greenhouse Solutions is hosting a full day course at The Aquaponic Source on Sunday, October 16 (can be combined with the Aquaponics Basics and Build Workshop on Saturday, October 15). Register here for the course!
For more information on Ceres’ greenhouses and consulting services, visit ceresgs.com.