戀上養耕共生
Hooked on aquaponics
Brattleboro couple spreads the word about a more sustainable way of raising plants and fishBy Alexandra Ossola/The Commons
BRATTLEBORO—For visitors to the home of Mark and Susie Crowther, the blue plastic barrels can be the elephant in the room.
What are those barrels doing in a room of their own, people wonder, and why do they keep emitting sounds of rushing water?
They’re aquaponics systems — closed, symbiotic systems in which the Crowthers can efficiently raise plants for their consumption and fish, using recycled materials and water.
Aquaponics is gaining traction on a larger scale as an alternative to traditional methods of produce and fish farming. In developing countries with a limited water supply, people like aquaponics guru Travis Hughey are introducing the concept as a way for individuals to grow their own food while making the most of their limited resources.
Thanks to some research, seeds, water, fish, and a bit of creativity, Mark Crowther has become an avid aquaponics hobbyist, and he is working with the Bonnyvale Environmental Education Center (BEEC) in West Brattleboro to host two workshops in May.
Aquaponics has been used for centuries, as far back as the Aztec empire, when engineers from Tenochtitlan created floating islands of reeds on which they planted seeds for fruits and vegetables.
These days, though, the systems can be as large as lakes or portable and small enough to fit on a tabletop indoors.
To Crowther, the key to creating these systems is to tailor them to the space available; each one of his systems is built from several 55-gallon blue plastic barrels, one sitting cylindrically on the floor as a tank for the fish, the other half-barrel placed perpendicular on top of the other, as a larger plant bed.
There’s a large hole in the bottom barrel above the waterline so that he can access the fish (in Crowther’s system these are golden shiner minnows, “because they were available at the local bait shop,” he said).
The top half-barrel is full of expanded shale, which is Crowther’s “grow bed media” into which the seeds were planted.
This grow bed media is essential in any aquaponic system because it houses those bacteria that enable the plants to absorb the nitrogen. He chose the shale because it’s lightweight, porous, and local.
“But the grow bed media can even be free,” Crowther said. “You can just go down to a brook or river and pull out a bunch of pebbles.”
The final key component to this system is a small electric pump that brings the water from the fish’s bottom barrel to water the plants on the top barrel. A simple bell siphon then flushes the water back down to the fish tank once it fills to a certain level.
The nitrogen cycleThe concept behind aquaponics is based in the nitrogen cycle, which many of us learned in middle-school science class.
Nitrogen in the soil that was deposited by precipitation takes the form of nitrates, which plants need to grow. (Fertilizers incorporate nitrates for this reason.) All fish excrete ammonia, a nitrogen compound, which can kill them if it accumulates to too high a concentration in the water.
Plants are able to absorb that ammonia in the water with the help of the bacteria nitrosomona and nitrobacter. Because the water is recycled, a closed aquaponics system uses approximately 90 percent less water than traditional farming methods, and the system allows both the fish and the plants to exchange nitrogen to their mutual benefit.
Crowther’s interest in aquaponics came about as a synthesis of many other lifelong interests, primarily with aquariums, gardening, and science.
“[I saw aquaponics as] a way of getting back into traditional gardening and incorporating my passion for being an aquarium hobbyist in the past,” he said.
“We love to farm, but the drawback of traditional farming in Vermont is that once you harvest your food, you don’t get to start up until the following spring,” he added.
“With aquaponics you can grow a wide variety of crops year round,” Crowther said. “I thought maybe it would be interesting to get the fish into the system and farm in a way where I didn’t have to pull a weed.”
Crowther primarily grows cool-season vegetables — lettuce and a few spice plants (including mustard and cilantro) — in his system.
While his system is too small to raise fish that could be “table-ready” (that is, suitable for human consumption), larger systems could incorporate harvestable fish (trout, tilapia, perch, etc.).
Crowther preferred his first system to incorporate local species, which meant that they had to be cold-water fish.
With issues of overfishing from the world’s oceans and the myriad problems associated with fish farming (including larger environmental impact and escapement), aquaponics can seem like a panacea for those who raise fish.
However, the question rapidly arises if the artificial lights, pumps, and materials used in an aquaponics system are more cost effective than the fish and produce grown by more conventional methods used to raise the food that now appears in grocery stores.
Crowther believes that the best way to make these systems economically viable is to suit the systems to their climate; he intends to move his systems outside during the summer, replacing the artificial (and costly) heat and lighting with sunlight.
Tilapia has become popular with fish farmers because they “grow so quickly and reproduce like crazy,” Crowther said, but this type of warm-water fish would require too much heat to be viable here in Vermont.
Cold-water fish like perch and rainbow trout are better suited to the climate, and they still grow large and fast enough to be sold commercially.
To Crowther, aquaponics is ripe for taking hold in the region because “we are already invested in education, sustainability, and organic food and are confined to a short outdoor growing season.”
“Unfortunately, aquaponics has never gained ground on a commercial level in our area because of the brief exposure Brattleboro had to Carbon Harvest,” he said, referring to the currently stalled aquaponics endeavor on Brattleboro’s Old Ferry Road.
Carbon Harvest planned to grow tilapia and various types of produce, but has not gotten off the ground due to financial difficulties.
One of Carbon Harvest’s planning errors, Crowther said, might have been attempting to grow a warm-water fish, which meant that the entire building had to be heated to a tropical level that is simply cost-prohibitive.
“That was too bad for Brattleboro, but smaller systems could work for the community from more of a grassroots level, if not on a commercial level,” he said. “The idea is still worth spreading so people can see the value in farming this way.”
Crowther sees those who would be most interested in aquaponics as people who are interested in sustainable agriculture, who are curious about where their food comes from, who respect nature, and who want to bring some of it into their homes.
With some plans pulled from the Internet, some creativity and a do-it-yourself attitude, anyone can construct an aquaponics system.
“One advantage of this is that it’s not an elitist undertaking,” he said. “You don’t need much money to get started.”
Crowther is working with BEEC and Transition Putney to host workshops at the Putney Public Library on Wednesday, May 15, at 7 p.m., and Sunday, May 19, at 1 p.m., on aquaponics. Participants will learn how to construct their own portable aquaponics systems, and all ages are welcome.
“Once kids figure out that you can very easily adapt an aquarium to grow lettuce with a simple 10-gallon tank and a 5-gallon bucket, they’ll realize that it’s fun to watch things grow and will be interactive with this whole process,” he said.
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