Earth Solutions explores the future of farming with its Farm in a Box™.
The buzz started last spring in Cabbagetown as Dr. Dave, began exploring a new type of organic gardening in his backyard, aquaponics.
“It was on the front porch so neighbors who heard the water and saw the rain barrels and plant beds made from salvaged metal roofing started asking questions.” Park Pride asked me to consider a grant proposal for expanding the system to a local Community Center. Soon after, a string of state and national news outfits began to write and film stories.
“It was NPR by the time I had moved took the idea inside and when spring arrived Atlanta’s Fox 5 and the Clark Howard Show followed the progress in the backyard.
“When The Wall Street Journal called it took my breath away and I realized that this was a really big story. But the biggest was when I found myself on July 4th, setting up the Farm in Box for Good Morning America in Central Park. “
It had been only one year since Earth Solutions founder had downloaded his first set DIY aquaponic plans the company’s version was being broadcast across the country. This more than anything is a testament to the enthusiasm aquaponics creates and the novelty of a design that ads the element of fish to the garden, indoors or out.
-Dr. David Epstein
Farm In A Box
Having studied the different systems being marketed around the world, our product development group at Earth Solutions has created pleasing designs for indoors and out, making aquaponics accessible to everyone. Placed in educational settings, next to a home window or in public spaces the Farm in a Box gives but an example of the possiblities.
In doing so, Earth Solutions has designed 4 aquaponic Farm in a Box models and has two more in development. These include the Little Tokyo (as seen on Good Morning America), the Sydney, Grand Cayman and the Phoenix. Originally we launched these with wooden tanks but realized that glass was more experiential and created more educational opportunities.
Earlier models were made from FSC certified pine, to save on cost, but required paint or finish to leave outdoors. Newer models are of FSC Certified cypress which is more water tolerant. Rather than relying on PVC containers we are using EPDM rubber to create a water tight bed liner. This is the most stable form of pond liner and is recognized as the best material in aquaculture. These systems are available at Earth Solutions website and by taking advantage of our Holiday Promo Code: AQUA2431you are eligible to receive a 15% discount through December 15th, 2009.
“These smaller systems are not merely convenient means of gardening on patio or indoors but they truly represent the future of gardening. As our world’s population rises and resources of fish and farmland diminish we have no choice but to redefine how we feed ourselves. Aquaponics is one very important step to our sustainability on this very small planet. By taking responsibility to feed ourselves on an individual and community level we can wrestle the task of farming away from the agriculture industry which will has already become overburdened. By teaching our children how simplified garden methods exist, we will have sown the seeds to our survival.”
- Dr. David Epstein
“Wow! This makes gardening fun and educational!”
“I can create an entire science curriculum around this system!”
These were some of the comments we heard as people visited our booth. The children
were particulary taken which supports our goal of using our aquaponic systems in educational settings.
Remember, Aquaponics works best when people work less!
Follow us as this exciting story continues in 2010!
Be a part of the earth’s solution.
Aquaponics is a method of gardening that utilizes relationships that exist naturally between fish and plants. Functionally it is the merging of aquaculture (fish farming) and hydroponics (soil less gardening). Yet energetically the efficiencies created to producing organic vegetables and organic fish are remarkable:
- No fertilizers or organic compost required
- No pesticides to manage soil born disease
- Less labor – No weeding or soil amending, above ground cultivation.
- Minimal water use, yet plants remain continuously hydrated
- No effluent waste discharged
- Minimal energy to run systems
While aquaponics is still in its infancy, large scale operations are already in full production in Canada, Australia, Mexico, Israel and the US. The greatest body of research comes from the work of James Rakocy at the University of Virgin Islands. Domestically Growing Power in WI provides demonstrations and workshops.
Twenty Best Crops Ranked by CSPI Nutrition Score. This info is from the Center for Science in the Public Interest (CSPI), collated by Robert Arnot, M.D. CSPI scored each vegetable by adding up its percent of the US RDA (recommended daily allowances) for six nutrients plus fiber (Vitamin A, C, folic Acid, iron, copper, and calcium). They used a slightly different but similar scoring scheme for each food category (vegetables, fruits, beans, and grains).
1) Sweet Potato
3) Spinach, raw
4) Collard Greens
5) Red Bell Pepper, raw
7) Dandelion Greens
9) Brussel Sprouts
10) Potato (Baked, with skin)
11) Winter squash
12) Swiss Chard
13) Snow Peas
14) Mustard greens
16) Romaine Lettuce (1 cup)
19) Green Bell Peppers
Best Fruits (These were ranked according to Vitamin A, C, folic acid, potassium, and fiber).
10) Watermelon (2 cups)
11) Raspberries ( 1cup)
12) Grapefruit, red or pink
14) Grapefruit, white
15) Honeydew melon
18) Star Fruit
20) Cherries, sweet
2) Pinto Beans
3) Chickpeas (garbanzos, ceci)
5) Cranberry beans
6) Black-eyed peas ( cowpeas)
7) Pink beans
8 Navy beans
9) Black beans (turtle beans)
10) Small white beans
11) White beans
12) Baby Lima Beans
13) Kidney beans
14) Adzuki beans
15) Great Northern Beans
16) Mung Beans
17) Lima Beans, large
18) Broad beans (fava beans)
19) Peas (split, green)
20) Tofu, raw, firm
2) Whole wheat macaroni or spaghetti
4) Buckwheat groats
5) Spinach Spaghetti
7) Pearled barley
8 Wild rice
10) Brown rice
13) Wheat berries
16) Rolled oats
18) Converted white rice
20) Instant White rice
Written by Niall Fahy of RealitySandwich.com
What if we were to grow food, demonstrate the principles of sustainability, and provide green education and employment in our own neighborhoods?
An Australian sustainability collective has come up with a novel approach to bringing ecological organic food production into our cities. Their design is fast, efficient, cheap, demountable, and scalable. Welcome to the urban farming revolution proposed by CERES.
Cities, in the normal scheme of things, suck inordinate amounts of resources from the surrounding countryside. They are massive energy sinks, guzzling power and food while producing tonnes of carbon dioxide and waste. Moreover, the city limits demarcate a perceived division between synthetic and natural — between the high speed sophistication of modern civilization and the relative placidity of agrarian life. We often tend to think that in our living arrangements one has to largely forsake one’s connection to either culture or nature.
Climate change and the approach of peak oil will demand localization of food and energy production. With this in mind, CERES (the Center for Education and Research in Environmental Strategies) — a community based model of sustainable society in the metropolis of Melbourne, Australia — plans to build a number of modular high-density organic farming hubs on disused pieces of land throughout the city.
These intensive urban mini-farms are designed to be highly productive, energy efficient, customizable, and cheap to build using shipping containers and plastic poly-tunnels. Incorporating aquaponic vegetable cultivation, fish farming, mushroom production, beehives, and a food processing and distribution service, the farms are designed within the permaculture ethos of mimicking nature’s flows. The waste of one process becomes fuel for the next, and each stage of the process yields a product.
Aquaponic farming means that water (rather than soil) is used as a medium in which to grow plants. In an urban setting, this solves the all-too-likely issue of soil contamination due to industrial pollution. In the CERES model the aquaponic system will be fertilized using water pumped from the fish farm beneath, which is rich in nutrients from their waste. The fish are fed vegetable scraps and worms grown in mushroom compost. Root systems of tomatoes, cucumbers, eggplants, leafy greens, strawberries, sprouts, and herbs will in turn clean the water before it recirculates to the fish.
Biodigesters that can decontaminate organic waste and turn it into usable energy are another potential component of this rapid-turnover design, as are solar panels and a water harvesting system. The food distribution area — which will operate as a co-operative — could also function as a café, education center, and community social space. As no permanent structures are built, the need for planning permission is eliminated, making the hubs easier to implement and also more palatable to any property developers or government bodies that may end up being involved.
One of these farms can be set up within a week, and the first will be installed in Melbourne in early 2010. The project’s proponents want this to be the first of many, and are talking to the local Office of Housing and Schools, seeking pieces of land that will be available for as little as three years. And they can’t wait to see what people around the world will do with their idea. The hubs will be intended to inspire people all over the world to follow suit and refine the designs to fit their own local needs.
Given sufficient opportunity, the concept could provide a significant portion of the city’s food while providing education and employment for hundreds of urban farmers and installers. Through being empowered in this way, communities can become more self-sufficient, not to mention happier.
Central to the concept is that sustainability initiatives are located in a participatory social setting. At CERES this entails community arts and music festivals, an organic garden and market/food co-op, a plant nursery, a bicycle workshop, a café, community and school gardens, an energy park, weekly sweat lodges, and numerous experiential education programs.
The vision is that sustainability need not entail a return to antiquated ways of living, but can merely mean the incorporation of innovative technology into a respectfully treated environment. This sharing of their aspirations for urban farming is one way they hope to tap into the global community’s yearning for reconnection with the Earth, feed their neighbors, and help to make our cities places where nature is not absent.
Earth Solutions deeply resonates with this article and the spirit of this movement. We plan on expanding our current Village in a Box product line by adding biodigesters, spirulina ponds and other sustainable living tools. Our goal is to provide resources for people to lift their ideas into action and become more deeply integrated in the care of our planet and our communites.
Image by nicolas.boullosa, courtesy of Creative Commons license.
How do I add plants to the system? Plants may be added by either directly seeding, clippings, divided root stock, seedlings or transplanting larger plants. Each is very effective. Direct seeding is even practical for sprouting sunflower seeds or raising wheat grass. Clippings may be taken from other plants, just below the knuckle of green, non woody clipping. Divided plants merely should be separated, roots untangled and rinsed of any debris and plant into the rocks. Seedlings and transplanted plants must have their roots rinsed of all dirt. This may be more difficult from tightly bunched roots in contained plants. Roots may have to be trimmed back if they are filled with dirt and are larger transplants. It is a good idea with transplants to shorten the top of the plant by 1/3rd and remove any dead or unhealthy roots. This will invigorate the plant and allow more water and nutrients to reach all the leaves. Clippings are best managed by cutting 1” below a knuckle and directly inserting to the rock bed, without hormone or fertilizer. The leaves should be trimmed back by pinching the lower larger leaves or cutting them in half horizontally. Leaving two to six small to medium sized leaves is all that are required for most plants. Roots will develop quickly.
How many plants can I plant at once? In a Little Tokyo sized system, you may plant between 6 to 8 plants. Space them to allow for growth and if some outgrow the area, clip them back and eat (if edible) or transplant into another system, or in the ground. For larger plants you may start with one to three plants. All plants may be trimmed back or divided at the roots. It is not a problem to lift the plants out of the rocks and divide the roots, as long as they are not left out to dry.
What about water plants? Water plants are helpful for many reasons. Fish tend to be less aggressive towards each other when plants are in the water that they like to eat. Anacharis and water hyacinth are ideal. These plants also add oxygen to the water.
What plants can I grow? These systems will accommodate almost any vegetable, herb or flowering plant. Larger fruiting plants and heavy feeders, including tomatoes, cucumbers, eggplant, broccoli and melons will require more sunlight and more fish to ensure enough ammonia is produced. Light feeding, can be raised with fewer fish, and includes leafy greens including arugula, lettuces, basil, strawberries, mint, chives, parsley, cilantro, peppers, sprouts and okra. Flowering plants will grow but if they require bees to fruit (ie strawberries) then you’ll need to be sure to raise them outside.
What ratio of plants to water to growing area is ideal? Light feeding systems do not require too many fish; 1 pound of fish need about 2 gallons of water and will produce enough organic nutrients for 4 square feet of growing area.
If the new leaves on my green plants are yellow what can I do? If your plants are starting to go yellow it is most likely because your system is low in Iron. Add some Chelated Iron to your system. A teaspoon of Chelated Iron mixed in a bucket of water and added slowly into your grow beds should do the trick. You might notice your system goes black or very dark in colour after you do this. That is fine, don’t worry about it and it will clear in a few days.
What causes the plants to wilt? If they are getting too much water and not enough sunlight they will wilt.
What are some reasons why my water may be murky? The rocks may not have been properly cleaned. Feeding fish too much may cause murky water. You’ll know if you fed too much if they don’t eat everything you’ve fed them within half an hour. Too much light exposure on water causes algae to build up. Putting anacharis or hyacinth can remove much of that problem; or you can do a water exchange and take out 50% of the water and replenish it. If you have tested it and the ammonia and nitrite are not too high, then stop feeding the fish for a couple of days.
Can I leave the system outdoors year round? If you raise goldfish, they can withstand very cold temperatures, but a solid frozen tank will not be good. Plant roots will die if they freeze solid in a wet rock bed or in deep water culture. If you live in a tropical climate you can raise fish and plants year round. Since many people live in climates where the winter water temperature will drop below 50 degrees; at that temperature tilapia and many other fish will not survive. Winter plants (broccoli, cauliflower, kale, beets) will do okay, as long as the roots don’t freeze and there is a source of fish waste. In outdoor winter settings it is best to use goldfish and turn off the pump when the temperature goes below freezing. You should leave an aerator on so that a frozen tank will still supply air to the fish.
Can I put a heater on in the winter? Yes but if it is an AC electric heater, you may see a significant rise in your heating bill. The best way to handle the winter is to either use the smaller Farm in a Box™ systems indoors or to enclose your Phoenix in a greenhouse and heat with a heating system or use solar panels or passive solar heat capture.
Do I put fish and plants in the system on day one? It is best if you let the system cycle for a few days before adding fish and plants. In order to remove fish ammonia, there needs to be a healthy colony of nitrification bacteria in the rock beds. This colonization can be stimulated by adding a capful of ammonia to the water. Once in the rock beds the health bacteria will naturally populate the area, paving the way for fish and their ammonia waste. Plants will do best if there is some nitrogen in the system too. This is not so much a concern at the early phase as plants are small and don’t require a lot of minerals. But if you plan to transplant a larger plant into this system, then stabilization is a good idea. As the plants grow, the fish will be growing and the nitrogen levels will rise to the occasion.
Do I need to add fertilizer? No never. It will kill the fish. And if it’s not good for the fish, it’s probably not good for the plants. Organic food tastes better anyway.
How do I test the pH and nitrogen levels? There are a number of freshwater test kits available; you may buy them online at Earth Solutions or purchase at your local fish store. For larger systems you may want to use an electric device to read pH and temperature. The smaller systems generally do not have to be monitored. After a couple weeks a normal balance will occur. If there is a lot of ammonia in the system, more bacteria will colonize to make that conversion and the plants will grow more as they absorb the extra nutrients.
Do I need to add air or oxygen? In the smaller systems adding oxygen may be helpful but is not necessary. Because the water flow forces air into the tank oxygen is provided through that movement as it occurs every 1 hour or so. In larger systems, producing a lot of waste and growing many plants, oxygen addition is very important.
If I have my system outside, does the rain throw off the pH balance? The pH in an aquaponic system should be maintained between 7.0 and 7.5. If your pH is higher than 7.5, this is usually ok and you do not have to do anything to ‘fix’ it. The nitrification process will cause the system to become more acidic over time. We have had systems with pH levels just over 8 when they started and they all went down over time. If your pH drops below 7.0, the nitrification process will slow dramatically and stop by the low 6′s. It is important that you do not let this happen!
How do I buffer the system if it’s too acidic? You can increase the pH of the system (make it more alkaline) by adding calcium carbonate. But be very careful; this is really only necessary in larger systems. Add a small amount of the powder to a bucket of water. Then pour in a teaspoon at a time, once per hour and test the system before repeating. Remember it is very alkaline so do not just dump it all quickly into the system. If you place sea shells under trickling water in the system then calcium will slowly release into the system providing a mild steady buffer, preventing any need for alkalinizing with calcium carbonate.
Should I worry about eating plants raised on fish poop? There have been no known incidents of contamination of plants by fish water in aquaponics. However it is always a good practice to thoroughly wash your plants before eating, no matter the source. Salmonella is not typically a problem in fish tanks; it is more common among turtles and fowl. Birds fly over these systems and will occasionally land on the bed for water or strawberries, and poop. Again, wash your plants whenever you grow your own or acquire from grocery or another gardener.
How do I clean the glass if it gets algae buildup? Best way is to take a non soapy scouring pad and scrape the walls clean. If the bottom of the tank builds up too much mirkyness you may stir up the water a bit and let it get pumped up to the upper beds where it will filter through the rocks. Or you can buy a siphon pump to clean the debris from the bottom of the tank. Try not to clean the system too much as the debris is helpful to maintain bacteria for nitrification.
Will the Farm in a Box withstand moisture? The wood is untreated and will last longest if painted or treated with linseed oil.
What sort of plant lighting is necessary? For outdoor plants, 4-6 hours of direct sunlight is ideal. Herbs and light feeding plants will do okay with 2-3 hours of direct light. Indoors, plants should either be exposed to a south facing window or else a grow light can be placed above the plant beds.
Fish lights? Fish do not require much lighting. If you are raising water plants in the same tank as you are growing fish, it is necessary to get sunlight to the tank so that they may photosynthesize and produce oxygen. Algae forms when there is too much direct light on any nutrient rich water source.
Can I leave the system outside? Except for the larger Phoenix system, try not to let your system get wet from rain. The fish tank may flood causing you to lose fish. Rain exposure will also dilute the nutrient concentration, can cause pH to become acidic and if unpainted or varnished, the wood may warp and discolor. We will offer the designs in marine plywood or cedarwood which is weather resistant. The Phoenix is built with cedarwood and marine plywood.
What do I need to do for the system if I go out of town? Goldfish can survive for days without food but if you want to be sure there is steady nitrogen production and happy bacteria colony, you may want to buy an automatic fish feeder.
How often should the water cycle on and off? In an ebb and flow system the water can go on ss frequent as once per hour or to as infrequently as once per six hours. This depends on the rate at which the bed dries out and the needs of the plants.
Electricty: Please use CAUTION when handling electric outlets near water.
What’s the poop on fish selection for the Farm in a Box™ with glass tanks? For aesthetics, goldfish and tropical aquarium are popular in small systems. One may argue against goldfish and tropicals as they are not indigenous to our water systems and if by chance they end up in a lake or stream then they become competitive to local aquacultures.
Local Fish: Aquaponics is important as a means of supporting local food production. Any type of fish may be raised in an aquaponic system. But those that thrive in local conditions are ultimately best for promoting local aquatic culture, as they create value within the region. Another option is to catch local stream or lake fish (perch, crappy, bream, bass, catfish, minnows, gamboozia). For education, local derived, cost and purposes of protecting local water colonies, these may be best suited.
Tilapia: Tilapia are about the most popular fish raised and eaten in the US. They are a white meat with a good taste. They produce a lot of ammonia which makes them a good nitrogen source. They also have strong immune systems, rarely getting sick and they tolerate imperfect water conditions, which makes them easy to raise for newbies. However tilapia are tropical and do not tolerate temperatures below 55 degrees. In fact, they like it a very warm 80-90 degrees and grow fastest under these conditions when fed frequently. This means that outdoors, if the weather is not tropical where you are raising fish, then they will grow slower or else their water will have to be heated.
Crayfish: Another ideal source of nitrogen is crayfish. The red tip Australian crayfish also produces a lot of phosphorus, a nutrient important in heavy flowering and fruiting plants. Crayfish are fun to raise and do well in water as shallow as 4″ up to 18″. They are prolific reproducers and are an edible source of protein. Bream, crappy, bass and catfish are other obvious choices. These fish are somewhat more difficult to raise and not as tolerant to sudden changes in pH, temperature and oxygen levels. They grow more slowly than tilapia but are very popular in the american diet. These fish also require warm water to eat regularly and grow quickly and produce a good amount of ammonia. Salmon and other trout prefer colder water year round, though not too cold, and are not commonly produced in aquaponic system thus far.
Nutritional values: In larger Farm in a Box models appropriate fish choice includes those that are edible and provide good nutritional value. Omega 3:Omega 6 ratios and quality of fats are very important. On that standard, the most desirable fish are the Australian Silver Perch and Jade Perch; these have 10x (10:1) better ratio than does salmon (1:1) and a 100x (1:10) better ratio than tilapia. The problem is that these fish are not sold live in the US at this time. Salmon and trout are desirable but are too difficult to raise in captivity for non experts.
How many fish: The San Antonio, Dallas and Phoenix systems will support as many as 25 to 100 edible fish at a time. These fish will not all grow at the same rate, so harvesting for consumption is possible and may be done on successive weeks once they begin to reach maturity. Fish may be sorted by their size by using two or more 100-200 gallon tanks.
Where to get fish: Smaller fish may be sourced at local aquarium shops. Larger edible varieties may be netted out of creaks and ponds. For tropical and larger volumes of edible fish, including tilapia, Earth Solutions can help source them, or else depending upon the laws of your state or municipality, fish may be ordered from hatcheries and delivered by Fed Ex to your door. Quantities of 150 to 500 generally cost $0.50 to $1.00 per fish. For quantities under 150, you may expect to pay $2-3 each.
What to feed fish: Food for smaller aquarium fish can be purchased at the fish store. For larger tilapia a good quality salmon dog food is recommended. Purina makes a catfish food that is commonly used in fish farms and for tilapia. The quality of dog food is superior, though we encourage non-corn feeds, as most corn is genetically modified. Otherwise, raising worms (vermiculture) or soldier fly larvae from composting organic greens will guarantee that not only are your aquaponic vegetables organic but so are your fish. Considering the dire condition of our worldwide water supplies, organic fish is practically impossible to source and growing your own will be the most reliable source. Duckweed is a floating aquatic plant that is easily raised in pools of water for the purpose of feeding fish. Tilapia will eat as much as 25% of their diet in the form of this green protein rich food.
How often to feed fish: Goldfish do well to eat once every other day. Tilapia are heavy feeders and will eat as much as 3-4 times per day when water temperatures are in the 80’s-90’s. At this feeding rate, ammonia and fertilizer production is at its best. In colder weather, much lower feeding is the rule. The best way to determine how much to feed tilapia is to feed ad libidium. In other words, feed until they stop eating. For 20 or so tilapia that are between ½ and 1 lb, you may expect them to eat about 2-4 tablespoons of feed every 3-4 hours.
My fish are dying; What can I do? Often this is caused by either not acclimating the fish to the new environment. They should be added by setting the bag into the water so the temperature adjusts slowly. Then let in some tank water into the bag and repeat this every ten minutes or so up to about 30-45 minutes. If they are dying after having been in the tank for a day or so it may be because the rocks were not thoroughly rinsed. You may want to do a 50% water exchange. Be sure to use non-chlorinated water. If you are feeding the fish too much food, they may die as ammonia will be produced too abruptly. If there is no bacteria in the rocks because they did not have a chance to colonize then the ammonia will not be removed and fish will die from their own waste. Bacteria will colonize only under balanced conditions. They need aeration through the ebb and flow cycle and it takes up to a week with exposure to ammonia for them to colonize.
Where’s the Buzz? Saving the Bees with Aquaponic Gardening
S. Corey Thomas
For many backyard gardeners, the familiar sight of honeybees buzzing about the blossoms has been troublingly absent in recent years. Since 2006, a mysterious syndrome called colony collapse disorder (CCD) has taken a heavy toll on bee populations around the world. Though they have many theories, scientists are still unsure of the primary culprit behind the mass disappearances.
A new documentary airing on the Planet Green network takes a closer look at the precarious state of honeybees and their human handlers. The Last Beekeeper follows three American apiarists struggling to weather the hardships of collapsing colonies in a depressed global economy. At stake are not only the livelihoods of the beleaguered beekeepers, but also the harvests of a wide array of fruits, vegetables and nuts that stock our pantries. Foods from strawberries to almonds rely entirely on the nomadic bees, trucked across long distances on flatbed trailers to pollinate the seasonal crops.
Colony collapse disorder brings to light just how vulnerable and unnatural we’ve allowed our centralized food production to become. Without the annual transportation of thousands of beehives across the country, many crops would never yield their fruits and grocery store shelves could quickly go bare. Monoculture farming and urban sprawl have added further stress to honeybee populations, eliminating the diverse, wild habitats that support pollinator insects naturally.
Aquaponics provides a sensible solution to many of these problems. By localizing food production in our own communities, we can ensure our connection to sustenance in times of uncertainty. Including bee-favored plants such as rosemary, lavender, and oregano in our aquaponic gardens helps to attract and support native honeybee populations, which in turn keep the plants healthy and fruitful. And as we recently discovered in the large system in Dr. Dave’s backyard, these aquatic ecosystems can double as a cheerful watering hole for thirsty bees!
The symbiotic relationships established in aquaponics – from fish to plants to helpful insects – are complex, and endlessly surprising. By modeling our gardens on nature, we avoid the pitfalls of a collapsing industrial culture, beehives and all, while benefiting from all the wisdom of the earth.
Check out this video of busy honeybees stopping by Dr. Dave’s aquaponic garden for a drink:
Tips for Growing Duckweed
Where to get duckweeds?
Duckweeds are available from many sources.
How to handle duckweeds?
Duckweed plants are delicate and easily damaged by fingers, forceps and other instruments. Individual plants and small colonies may be picked up and moved without damage using a bacteriological loop. Just place the loop in the medium beneath the plant and lift up. To collect larger quantities of plants, use lightweight screening material to net the plants from below. Fiberglass screen material is available in hardware stores. Alternatively, fabric stores sell strong, light-weight netting used for making veils. Duckweed roots are sticky and will adhere to screens and nets, so it may be necessary to gently scrape the plants off the net with a knife or a thin spatula.
How to grow duckweeds?
Growing duckweeds is like growing any other plant. Moderate conditions of temperature and light and a liquid medium with the necessary nutrients are essential for good growth. Fortunately, duckweeds adapt well to a wide range of conditions and are easy to grow.
Duckweeds can be grown in the pond water from which they were collected in open containers. It is important to replace the water frequently, since evaporation will result in concentration of salts. Using open containers prevents overheating if you place the containers outside or in a sunny window. See below for more about lighting duckweeds for the best growth.
In nature duckweeds grow in water from many sources and compositions. They can be grown in artificial pond water or in diluted aquaculture media, such as Hoagland’s solution. It is important to provide a source of chelated iron and to adjust the pH to the optimal range.
It is important to keep your duckweed cultures clean. If you collect fresh duckweed specimens from nature, the water will contain a variety of other organisms. These will include bacteria, fungi, algae, protozoa, and even small multicellular animals and insect larvae. You can clean up your duckweed cultures by transferring the plants individually to clean fresh water. Remove damaged and aged (yellow or white) fronds from your cultures as they appear.
Native populations of duckweeds may be mixtures with varying genetic compositions. For serious work it is advisable to start cultures from a single clone. This will help increase uniformity for experimental work. It is easy to clone duckweeds.
Lighting duckweeds for the best growth.
Direct sunlight is a natural condition for duckweeds. Duckweeds commonly grow in open ponds or shallow wetlands with little or no shade. However, direct sunlight can be a problem if you grow duckweeds in small containers. Sunlight will warm the water and cause evaporation. Replacing the lost water frequently (not just topping off the lost volume) is important. Otherwise, you will gradually concentrate the salts in the growth medium. Duckweeds are freshwater plants (glycophytes) that do not tolerate high salt conditions. Plants grown in covered containers may not lose water from evaporation, but under direct sun the interior will overheat, bleaching and killing the plants.
Indirect sunlight, from a north window or skylight may be an acceptable light source, but growth may be slow, particularly if the days are short and there is much cloud cover. If you use indirect sunlight, remember that radiation cooling can be a problem at night during the colder months. Radiation cooling results from the difference in temperature between the plant (room temperature) and the night sky (very cold). Radiation cooling will slow duckweed growth, although most duckweed species are not damaged by cool temperatures. It may be necessary to cover the window at night to prevent excessive cooling. [ Read how greenhouses work. ]
Incandescent light bulbs are a poor choice. A major fraction of the light that they emit is in the form of infrared radiation that will directly overheat your plants. It is hard to obtain sufficient light from incandescent lamps for good photosynthesis without overheating, so they are not recommended.
Fluorescent lights are recommended if closed culture vessels are used, or if a sunny window is unavailable. Unlike incandescent bulbs, fluorescent tubes produce much less infrared energy. Most labs use two to four F40cw tubes in simple fixtures (often sold as shop lights) hung roughly 30 to 50 cm above the cultures. These conditions will supply sufficient light for photosynthesis and plant growth without overheating the plants.
Newer compact fluorescent fixtures that combine a twisted fluorescent tube with an electronic power supply in a screw-in base are especially convenient for building small duckweed growth areas. These fluorescent fixtures are also available in reflector mounts like floodlights. Plans for building an inexpensive portable plant growth stand are available.
Different duckweed species grow from the Arctic and Antarctic Circles to the Equator and from sea level to the high mountains. However, different species are better adapted to various temperature conditions. If you are going to experiment with duckweeds outdoors, you may be more successful with a locally gathered species than with a culture from a stock center.
Duckweeds can tolerate hot midday air temperatures if the water on which they rest warms more slowly than the air. Thus, a deep container (like a bucket) will be necessary if you want to grow duckweeds outdoors in hot weather.
Under cool cool conditions, duckweeds may form dormant buds, called turions. Duckweeds can overwinter in frozen ponds as turions or seeds. Freezing vegetative fronds will cause frost damage, as in other plants.
Studying the effects of stresses, like high or low temperatures, is an excellent subject for research.
Landolt, E. and Kandeler, R. (1987) The family of Lemnaceae – a monographic study. Vol. 2, Phytochemistry, physiology, application, bibliography. Veroff. Geobot. Inst. ETH, Zurich, 638 pp.