What is aquaponics one might ask? Though it seems like revolutionary new technology, humans have used the help of fish to grow their crops for thousands of years. From Aztecs floating crops on lake Texcoco in the ancient city of Tenochtitlan to rice paddy fields in China, Thailand and Indonesia full of carp, eels and snails, people have taken advantage of the coexistence of fish, plants and although unknowingly, bacteria.
Modern aquaponics neatly combines aquaculture (raising fish) and hydroponics by using the plant’s root zone to purify the water by up-taking nitrates, with beneficial bacteria acting as a middleman to turn ammonia fish waste into nitrate fertilizer. It’s an almost self-sustaining system that only requires recirculation and aeration of the water and food for the fish. There are a handful of systems in function that grow aquatic plants and/or insects in a third tank to feed the fish, making them completely closed loop systems whose only physical inputs are air and light. These are sometimes referred to as permaculture systems and are also living science experiments that recreate significant parts of the carbon, nitrogen and water cycles as they occur in nature.
The class assumes a working knowledge of aquaponics in its participants and is mainly about how to grow pot, with a fishy twist.
The main nutrient provided by the fish is nitrogen, as nitrate, but the system is lacking in enough phosphorus and potassium for those high yielding plants we expect out of hydroponics. That amount of fertilizer would kill your fish, which is why aquaponics is generally used for plants like lettuce or kale that don’t require such high P or K.
Steve Raisner, teacher of The Aquaponic Source, knew about this issue and was experimenting with a wicking bed. Steve and Sylvia Bernstein, veterans in the world of hydro and aquaponics, said that when a friend of the company named Vlad Jovanovic visited them from Serbia, he told them about a system he had developed for growing peppers using aquaponics called dual root zoning. Dual root zoning “gives you multiple zones of control where you have a soil layer you can control separately from your aquatic layer without the two contaminating each other,” said Steve.
Imagine a water permeable pot with holes in it, filled two-thirds with hydrocorn and the other third with organic soil, and a layer of burlap separating them. The pot is placed in the aquaponic system so that the tank’s water only comes up to just below the burlap flap. As the plant grows, it will have some of its roots in the soil, and some in the hydrocorn. By figuring out how much water the soil in the pot can hold (by doing a few trials before you put it into use), you can feed the soil with enough P and K to keep your plants happy without contaminating the water the fish live in.
All about that bacteria
It’s no news to the organic growers out there, but good fertilizer is all about beneficial microbes, especially with aquaponics. Nitrifying bacteria stand between the fish and plants to turn ammonia fish waste into nitrate fertilizer. These bacteria are naturally occurring but there are products designed to jumpstart your system’s bacteria population.
The dual root zoning method further expands the system’s microbial biodiversity with bacteria living in the soil, which help prevent root rot and other diseases by competing with them for nutrients. The bacteria excrement is itself the best fertilizer, according to Steve. The soil layer is fed with just the right amount of water and organic nutrients, and the water reservoir as a whole gets supplemented with small amounts of DTPA chelated iron and Epsom salts to provide Fe, Mg and sulfate for the entire system, fish included. The pH needs to be kept at 6.8 for the bacteria and fish to thrive, but miraculously enough this does not affect the plants’ absorption of essential elements.
The tilapias are fed with fish food certified for human consumption and supplement with insects and aquatic plants they raise and grow themselves. The fish in an aquaponic system are perfectly edible; just guess what they had at the Aquaponic Source company Thanksgiving dinner.
Putting it to the test
So it works with peppers and lettuce but, how about weed? After trying the dual root zoning system with one plant, Steve decided to do a little experiment. He took two clones of the same plant and grew one out with traditional hydroponics, and the other with dual root zoned aquaponics. Both were taken all the way to harvest and the yields were almost exactly the same. Okay so there were 1.5 grams more of the hydro bud, but those are spectacular results for such an experimental system. More messing around with it and he started to consistently get results on par with or better than traditional hydroponics. The flavor of bud grown this way is also much more earthy, sweet and natural than normal hydro. And no, there’s no taste of fish. They are growing Durban Poison x ISS Hybrid, Blue Hash and OG Kush with phenomenal results. One plant that’s about to get harvested is nine feet wide and almost five feet tall.
The class is Sunday, September 28th and runs from 8am – 5pm. It’s part lecture, part hands on and will cover starting a plant from seed or clone, propagation, pruning, trimming, nutrients, pests, air-flow, grow room specs, grow room security, flowering, hash-making and also goes over local and state laws to make sure everyone is legal, can’t forget that one. The class isn’t about aquaponics, it’s about how to apply this great technique to the cultivation of cannabis. However, it will teach you about dual root zoning and how to maximize the amount of beneficial bacteria.